In order to extend the signal transmission distance, facilitate the detection and noise reduction, and retain the signal energy as much as possible, the carrier suppressed single sideband(SSB-CS) signal output can be realized by phase shifting method. Using pilot method to control commercial lithium niobate double parallel (IQ) modulator can achieve the above goal. The experimental results show that the carrier to side ratio and side to side ratio of the output signal are greater than 20 dB in the range of 2-18 GHz. This method can effectively control the working state of the modulator without using the built-in photodiode (PD) of the IQ modulator, and the carrier side ratio and side side ratio can meet the expected SSB-CS signal.