The performance evaluation and testing for coherent principle based multichannel electronic systems such as MIMO communication, and phasedarray radar and multichannel reconnaissance receiver have always been complicated and expensive. Because the multichannel signals can be received is hard to stimulate. This paper presents a wide band phasecoherent multichannel signal stimulating method based on vector modulation technique, analyzes the influences of the vector modulator's non ideal characteristics on multichannel signals, and finally gives solutions. We propose a convenient and efficient simulation way for phasecoherent multichannel receiver testing by stimulating signals of wider frequency covering range, larger phase control range, higher precision and finer resolution.