The　wavelet　transform　character　of　step　response　of　second-order　system　was　studied,　then　an　integrated　performance　index　based　on　wavelet　transform　was　proposed.　Two　weighting　coefficients　of　the　performance　index　can　be　selected　freely　which　makes　the　performance　index　be　more　flexible　and　practical.　With　genetic　algorithm　and　the　performance　index,　the　optimization　of　the　parameter　of　PID　controller　is　quick　and　simple.　The　simulation　result　shows　that　the　integrated　performance　index　based　on　wavelet　transform　is　feasible.