Testicular torsion is the most urgent type of testicular disease and can occur from neonatal to old age. Neonatal and adolescent periods are the peak periods of morbidity. As a result of torsion of the spermatic cord, blood flow to the testis is impaired, which can lead to testicular necrosis and affect fertility if left untreated. Its prognosis is positively correlated with the degree and duration of torsion, so timely and correct ultrasound diagnosis is very important for prognosis. Ultrasound changes 1, testicular changes (1) within 6h, the two-dimensional sonogram can be normal, or diffuse hyperechoic, a few see the “bracelet ring” sign. The blood flow signal in the testis is reduced compared to the contralateral side. In children seen during this period, all testes survive. （CDFI shows no blood flow signal in the testis, and in some cases the blood flow signal is reduced compared to the contralateral side. (3) Beyond 24h, 2D sonography mainly shows enlarged testis on the affected side with uneven echogenicity and diffuse hyperechogenicity. Fissure-like hypoechogenicity can be seen, and the edges are depressed inward in a nibble shape. In those greater than 10 d, the enlarged testicle begins to shrink and may be smaller than the contralateral side, with hypoechoic, hypoechoic and inhomogeneous echogenicity, which may be accompanied by calcified spots. In a few cases, a hypoechoic “halo” begins to appear around the testicle, which is shown by color Doppler as a “colored halo ring”. 75% of the cases are left-sided torsion. Other changes (1) Changes in the head of the epididymis and the spermatic cord, the epididymis is diffusely enlarged and the echogenicity is uneven, with the head of the epididymis being more obvious. (2) Changes in the sphincter, scrotal wall thickening and testicular sphincter effusion. Acute torsion and subacute torsion of the syringomyelia can be seen as point-like strong echogenicity within the fluid zone, or separated echogenicity. In children with 6h-2 weeks of torsion, syringomyelia and hematoma formation are often present. (3) Change in position. In some children, the relative position of the testis and epididymis in the scrotum is changed to varying degrees. Testicular torsion is mainly distinguished from orchitis and epididymitis: early two-dimensional images are difficult to distinguish and mainly rely on color Doppler for differentiation. cdfi shows that blood flow decreases or disappears in testicular torsion, while blood flow increases in inflammation. It is important to note that when testicular torsion is released, local congestive changes can occur, which is a “rebound response” to reperfusion of ischemic tissue. Testicular torsion should also be differentiated from adnexal testicular torsion: 1. In adnexal testicular torsion, the testis appears as an inhomogeneous hyperechoic nodule between the testis and the head of the epididymis or next to both, whereas in testicular torsion, the testis appears as a strong echogenic mass above the testis and is much larger; 2. In adnexal torsion, the blood flow to the testis and epididymis is mildly increased, whereas in testicular torsion, the blood flow is reduced or absent. At present, ultrasound diagnosis of testicular torsion has become a clinically accepted test of choice. For children with clinical suspicion of testicular torsion, high-frequency ultrasound color Doppler is used. Color Doppler ultrasound can show abnormal testicular internal echogenicity and changes in blood perfusion, which can initially determine the degree of testicular torsion and identify other testicular and epididymal related lesions, and has important clinical value for the selection of treatment plan and prognosis. For children with clinical suspicion of testicular torsion, high-frequency ultrasound color Doppler should be the first choice for examination.