Abstract: Based on the grain yield data of regional trials with 233 winter and spring wheat cultivars (lines) in rainfed farmlands at 82 locations in four subregions of China in 2003-2009, this paper studied the experiment precision (EP), variety comparison precision (VCP), and testingsite discrimination ability and representativeness of national regional trials, and comprehensively evaluated the trial environment. The results showed that in onelocationoneyear experiments, the average coefficient of variation (CV) and the relative least significant difference (RLSD) were 6.1% and 10.5%, respectively, and in multilocationoneyear experiments, the CV was all within 8.2%, and the CV and RLSD were mostly well controlled, indicating that the trials had a high precision. The testingsite discrimination ability was the highest in the northwest spring wheat subregion, but showed less difference in the other subregions. The testingsite representativeness was the best in the northeast spring wheat subregion, and the worst in the northwest spring wheat subregion. On the basis of the comprehensive consideration of the testingsite discrimination ability and representativeness, and by using the parameters of the environmental comprehensive assessment (r_g-h) of GGE model, it was shown that the proportion of the ideal trial locations for wheat in our rainfed farmlands was only 32.4%. Among the wheat production regions, the proportions of the ideal trial locations were in the order of northwest spring wheat subregion (40.9%) > northeast spring wheat subregion (33.3%) > Huang-Huai winter wheat subregion (30.4%) > north winter wheat subregion (21.4%).