Abstract: Measuring rainfall quantitatively is one of the main purposes of dual-linear polarization radar. The rain intensity can be derived from reflectivity Z_H, differential reflectivity Z_DR and specific differential phase K_DP. The measurement accuracy of K_DP is very important for deducing rainfall. The measurement accuracy of differential propagation phase shift Φ_DP is calculated with various sample pairs M, range average intervals and spectrum widths σ_V by using theoretical formula. Then, the effect of those factors on the measurement errors of Φ_DP is analyzed. Those results show that standard errors of Φ_DP gradually decrease when the number of sample pairs M or range average interval increase, but standard errorsΦ_DP gradually increase withσ_V increasing (except in the case of σ_V=1 m/s). Moreover, three methods of obtaining K_DP from Φ_DP are summarized and the accuracy of those methods is compared. These results show that the errors of K_DP produced by the second method are very large; the standard error of K_DP can be less than 0.1o/km when using the first method and the third method on some conditions.