According to specific requirements of ground test for onboard control system, a simpler, with high load capacity and flexibility displacement sensor emulator is designed. The function of amplitude modulation is achieved by AD633 analog multiplier based on the carrier single, which greatly simplify the complexity of the hardware circuit. The load capacity is improved based on the non-linear degenerative feedback of operational amplifier and the current amplified function of audion. Also the use flexibility is gained by adopting effective user interface. The use results in a certain aircraft flight control system ground test shows that the designed circuit can achieve RVDT and LVDT signal simulation, which is with good electric characteristics.