Abstract: In order to decrease the power consumption of the electrooptical and resolve the high consistency with halfwave voltage of the inner MachZehnder (MZ) modulators in the phase encoder, using two biased MZ modulators, a 2bits electrooptical phase encoder for electrooptical analogtodigital conversion (EO ADC) was set up. The construction methods, features and performances of the 2bits electrooptical phase encoder were analyzed theoretically. The simulation results verified the feasibility of the 2bits electrooptical phase encoding method. The simulation experiments also fulfilled analogtodigital conversion for signals at 1 GHz with sampling rate of 12 GS/s. The analysis and simulation results show that the proposed method has low requirement for the consistency of the modulators and the input signal power is lower than 0.32 W. The analysis results also show that the quantization of the least significant bit is immune from the modulators directcurrent(DC) drift, while the decision uncertainty of the most significant bit influenced by the DC drift is lower than 3.8 %.