The primary detection of the MLC₂-chymase fusion gene transgenic mice was carried out by means of polymerase chain reaction(PCR) with two specific primers, which span across MLC2 promoter region and chymase structure gene region. The DNA electrophoretic bands of PCR products were recovered and purified, then sequenced by PCR sequencing method with one of the two primers. Final determination of the transgenic mice was conducted through comparing the sequencing results with sequences of transfered gene. This method is convenient, effective and specific.