This paper describes our approaches at NTCIR-12 short text conversation (STC) task (Chinese). For a new post, instead of considering post-comment similarity, our system focus on finding similar posts in the repository and retrieve their corresponding comments. Meanwhile, we choose frequency property of comments to adjust ranking models. Our best run achieves 0.4854 for mean P+, 0.3367 for mean nDCG@1 and 0.4592 for mean nERR@10, which reaches the top tier in official STC results.