The influenza A H7N9 virus is a highly contagious virus which can only infect poultry before early 2013. But after that time, it widely caused human infections in China and brought Southeast Asia great threaten in the public health area. The coding gene for polymerase basic protein 2 (PB2) in influenza A H7N9 virus encodes the PB2 protein, which is a part of the RNA polymerase. The enzyme lacks a correction function during its own replication process, so the mutation frequency of the influenza A H7N9 virus gene is high and the PB2 gene is also included. To investigate the codon usages characteristics of PB2 gene, gene sequences of 12 kinds of poultry are downloaded form the gene bank (NCBI) and their codon usage characteristics such as the effective number of codons (ENC), the evolutionary relationship of the sequences, the codon adaptation index (CAI), the correspondence analysis (COA), the relative synonymous codon usage (RSCU) and their PR2-bias are compared and studied. The value of these reults showed that there is a low codon usage bias in the PB2 gene. Then, the differences between the codon usages of PB2 gene from 12 kinds of poultry are compared and their potential applications are discussed. These results could lay a foundation for other further study on the evolution of H7N9.