A DGT (diffusive gradients in thin films) method for determination of 
phosphorus content on the basis of computer-imaging 
densitometry (CID) technology is as follows: a ZrO2 
phosphorus fixation film is assembled into a DGT (diffusive gradients in thin films) device, the DGT device is put in a 
phosphorus medium for phosphorus absorption, then the film is put in hot water of 85 DEG C for heat treatment for 5 days to promote further fixation of phosphorus absorbed by the film, the ZrO2 phosphorus fixation film is put in a colorant for coloring, a 
scanner is used for scanning of the 
colored film, 
software is used for converting image color obtained by the scanning into gray scale, and according to an established phosphorus accumulation amount and surface gray scale 
calibration curve of the ZrO2 phosphorus fixation film, the obtained gray scale is converted into phosphorus accumulation amount; and the phosphorus content in the phosphorus medium can be calculated by use of Fick's first law of 
diffusion according to the phosphorus accumulation amount in the phosphorus fixation film surface. According to the method, the CID technology is used to avoid 
slicing, extracting and other operation, and the phosphorus accumulation amount in the phosphorus fixation film, the phosphorus content in the phosphorus medium, 
spatial distribution and other information and can be quickly and easily obtained.