For comprehensive and objective evaluation the adaptability and stability for important agronomic traits of oat germplasm resources, 81 accessions of oat including naked oat and hulled oat were involved in this study, and genetic differences of seven important agronomic traits such as plant height in seven test sites were investigated and analyzed. On the basis of D value, a weighted subordinate function value, series of GGE biplot of genotype × environment were built with GGE biplot V6.3, and the adaptation and stability of 81 tested oat accessions in different test sites were analyzed according to distribution and relationship of oat accessions and test sites on above biplots. Results showed that grain weight of main ear was the trait with the largest variable coefficient among tested accessions of naked oat in all tested sites, and the number of effective tillers was the largest variable trait among tested accessions of hulled oat, and the rest five traits with no difference between naked oat and hulled oat. It was demonstrated that the method of weighted subordinate function in combination with GGE biplot would have good prospect in comprehensive analysis of oat agronomic traits. These accessions including Bayou No.3, 73014-336, Er Youmai, Bauntebue and Bayan No.1 would be cultivated well in the seven test sites at least, in which Bayou No.3 and Bayan No.1 have been selected as main oat variety in regions including Hebei Province. Such accessions as Jin 8609-1, LY03-02, Erqiu Youmai, 64 Yanmai, Pin 16, Banner and LY01-12 may be fit for breeding.