Based on the finite-differential beam propagation method and guided-mode analysis, the wave propagation characteristics of a AlGaAs/GaAs MQW electroabsorption modulator and multimode interference optical splitter are investigated. A novel wave-guide electroabsorption modulator incorporated with function of optical splitter is proposed and numerical simulated and experimental tested. The study results show that a wave-guide electroabsorption modulator with properly designed wave-guide thickness and length possesses features of optical splitter.