This paper presents an analysis and enhancement of efficiency in a class-E power amplifier using MEMS inductors. The MEMS technology is proposed and demonstrated by a prototype inductor. The model of MEMS inductors is created by HFSS simulator and its simulated result has good match with the measured result. Stacked-metal layer inductors in MEMS process are also developed to increase the quality factor. The simulation result of a CMOS class-E PA with MEMS inductors shows that the increased quality factor of inductors by 2 can improve the PA's efficiency by 6%. Furthermore, we present a design methodology for optimizing the PA's efficiency.