Men have two testicles, left and right, which can be similar in size or significantly different. This phenomenon of left and right not being exactly the same size de is very common in clinical practice. According to relevant surveys, two testicles of unequal size account for 30%-40%. Generally speaking, there is a certain limit to the size difference, and the possibility of lesions should be considered when the limit is exceeded. For the smaller side, we should consider whether there is any testicular atrophy caused by mumps, trauma, torsion, etc.; whether there is any mental varicose vein; whether the blood supply of the testicle has been damaged by hernia repair or other intra-scrotal surgery, etc. If the testicle is enlarged on one side, it should be carefully examined for chronic epididymitis, epididymal tuberculosis, testicular tumor, orchitis, etc. As long as the volume of one testicle is within 12-25 ML and the texture is normal, it will not affect the sexual function regardless of the size of the testicle on the other side, or even if it is removed due to disease.