Urine is one of the important excretions of the human body. Most of the metabolic wastes, toxins and excess water of the body have to be excreted through urine, and the kidney is the dedicated organ for generating urine, excreting urine and excreting toxins, and the whole process of urine excretion has to be completed by the kidney. When the kidneys are diseased, the urine will first change, the volume of urine is either more or less, and the composition of urine will also change abnormally. When protein, red blood cells, white blood cells and tubular type appear in the urine, it means that there is something wrong with the kidneys. Therefore, the change of urine is the barometer of kidney. When kidney disease is suspected, we should check whether the urine is normal first. If the kidneys are functioning normally, the urine is discharged smoothly, the amount of urine and the composition of urine are maintained in a normal state, and the toxins metabolized by the body are discharged out of the body in the usual way. Of course, urine cannot reflect all urological diseases, nor does it only reflect lesions of the kidneys. Urine may also change when there are diseases in other systems (such as fever, heart disease, diabetes, liver disease, etc.), and sometimes physiological changes may also cause changes in urine. Therefore, when kidney disease is suspected, it must be combined with medical history, symptoms, signs and other special tests to make a comprehensive analysis in order to make a correct diagnosis.