In order to meet the requirements of the design of radiation detectors, CdZnTe (or Cd1-xZnxTe) wafers grown by vertical Bridgman method w ere annealed in the vapor of In. The nature of this treatment is a diffusion pro cess, thus it is meaningful to relate the change of resistivity to the diffusion parameters. A transformation model correlating resistivity and conduction type of CdZnTe with the main diffusion parameter —— diffusion coefficient——is put forward in this paper. Combining the model with the analysis of our experimenta l data (namely DIn = 5.17 10-9, 2.625×10-10 an d 3.455×10-11cm2·s-1), the values of the diff usion coefficient of In in Cd0.9Zn0.1Te at 1073, 973 and 873K have been given for the first time, which coincide closely with those in Cd Te given by different authors. With the data, the effect of annealing time on th e change of resistivity and conduction type for Cd0.9Zn0.1 Te slice, which is annealed in saturated In vapor at 1073, 973 and 873K, have be en simulated and good consistency acquired. This work suggests an alternative wa y to determine the diffusion coefficient in semiconductor material, and also ena bles us to analyze the diffusion process quantitatively and predict the annealin g result.