In order to understand AAPB community structure and distribution in a high-frigid forest stream with cold environment, here, a field investigation was carried out in West Sichuan, China. Water was sampled in the stream at onset of the freezing period (FP), the deep freezing period (FPD) and the thawing period (TP). The methods of real-time fluorescent quantitative PCR and clone library were used to check the richness and diversity of AAPB. Temperature and other water characters were also observed to analysis the relationships between environment and AAPB. The results showed that low abundance (2.80±0.19)×10⁴bp/mL of AAPB was observed, at FP, but which rapidly increased to (4.65±0.30)×10⁴bp/mL at FPD, then reached to (5.79±0.19)×10⁴bp/mL at TP. Phylogenetic relationships from clone libraries displayed that Alphaproteobacteria classes dominated AAPB at FP, but Betaproteobacteria classes dominated AAPB at both FPD and TP. In addition, correlationships revealed that the concentration of chlorophyll a and dissolved organic carbon, as well as average temperature had closely relationships with AAPB abundance and diversity during the seasonal freeze-thaw period. All the results suggest that AAPB have low abundance but exhibit highly dynamical patters in the high-frigid forest streams and their communities share low homology with those in other freshwater.