By use of cluster variation method, a study of orderdisorder transition in A+2(B1/31B2/32)O3 system was carried out. Theoretical calculation indicated that the interaction energy parameter J had a great influnce on formation of both, the (B2/31B1/32)1/2 :B1/22 =1:1 mixed ordered domain and B1/31:B2/32= 1:2 domain, and predicted that it was more difficult to form the B1/31:B2/32= 1:2 full ordered domain relatively to the (B2/31B1/32)1/2B1/22 = 1:1 mixed ordered domain.