An interest in MSCM AM VSB CATV system is rising in China. In this paper we presents using EDFA and linearized external modulation for microwave subcarrier multiplexed （MSCM） lightwave system. And we adopt quantitative unconstrained numerical optimization method（simplex method） to optimize some key parameters of the system for the first time. So we provide a general method for MSCM AM VSB CATV system optimization.