Background: PSA decline is used as one of the treatment outcome of androgen receptor signaling axis targeting agent (ARAT) in general. However, correlation between PSA decline and survival outcome is not discussed enough. In this study we evaluated how PSA decline influence the survival outcome of ARAT against chemo-naive castration resistant prostate cancer (CRPC). Methods: A total of 200 chemo-naïve CRPC cases treated with ARAT (abiraterone acetate or enzalutamide) were included in this study. We investigated the relationship between PSA response rate and survival outcome (PSA progression free survival (PSA-PFS), Failure free survival (FFS) and overall survival (OS)). Results: PSA response rate correlated with PSA-PFA, TFS and OS significantly (p<0.0001, <0.0001, 0.0009, respectively). And we categorized PSA decline in four groups, group 1: no PSA decline, group 2: 0-50%, group 3: 50%-90%, group 4: over 90%. Median PSA-PFS were 2M (group 1), 4M (group 2), 10M (group 3) and 16M (group 4) (p<0.0001). Median FFS were 3M (group 1), 6M (group 2), 12M (group 3) and 27M (group 4) (p<0.0001). Median OS were 28M (group 1), 36M (group 2), not reached (group 3 and 4) (p=0.0056). In terms of OS, there is a big different between PSA decline <50% and ≥50% in survival curve. And we compare the factors influencing PSA decline ≥50%. PSA and age at initiating ARAT are significant factors predicting PSA decline 50%. Lower PSA and lower age correlated PSA decline ≥50%. Conclusions: PSA decline strongly correlated with PSA-PFS, FFS and OS in this study. It would be a surrogate marker predicting survival outcomes of chemo-naïve CRPC cases treated with ARAT. Further investigation is warranted to confirm these results.