Urine specific gravity test is to check the specific gravity of urine, if the specific gravity of urine decreases, it is urine specific gravity decrease, increase is urine specific gravity increase. The urine specific gravity drop is commonly found in urolithiasis and other diseases, it is appropriate to take the method of urine routine microscopy to examine patients with urine specific gravity drop. When examining urine specific gravity decline to be noted: 1, the urine specimen must be fresh, otherwise after a few hours of parking, red blood cells can be destroyed, white blood cells can be destroyed and pus urine disappears. 2, urine specimens must be clean. Women should wash their vulva, do not mix in the leukorrhea. If there are a large number of polygonal epithelial cells in the urine sediment, it may have been mixed into the leucorrhoea, it is appropriate to keep a clean urine specimen for re-examination. 3, urinary tract infection pus urine is often intermittent, so it is appropriate to repeatedly check several times before drawing conclusions. 4, after the use of antibacterial drugs, can affect the accuracy of the examination.