Free proline accumulation in plant tissues is a self-protection mechanism protecting plant from abiotic stresses. A P5CS gene was cloned using a candidate gene approach from wild soybean seeding treated with NaCl. Sequence analysis showed that, the full-length cDNA sequence is 2,232 kb, containing an open reading frame of 2148bp, encoding 715 amino acids. The cDNA sequence shared 98.79% similarity with PvP5CS1 from common bean. Real Time PCR analysis showed that the gene was significantly induced up-regulated expression by salt stress, the relative expression of the gene reached to the maximum at 200 mM NaCl treatment in roots and 300 mM NaCl treatment in leaves. And the expression models of GsP5CS gene were similar with the proline accumulation models in leave and root of wild soybean treated with different concentration NaCl. The above results showed that the cDNA sequence obtained in this study was the proline synthetase gene of wild soybean (Glycine soja), named GsP5CS.