Based on the comparation and analysis of phase compensation methods of 90 °space optical hybrid, two new methods were proposed. The first method is that 1/4 wave plate on the local oscillator laser branch is rotated to compensate for the phase difference and the first 1/2 wave plate on the signal laser branch is rotated to adjust the power ratio of I/Q branchs. The second method is that 1/2 wave plate and 1/4 wave plate on the local oscillator laser branch are rotated respectively to the calculated angle to achieve a predetermined phase difference and power ratio. The simulation analysis and system experiment of the two methods were carried out. The results of the first method show that when the angle between 1/4 wave plate fast axis and x axis varies from －10° to 10°, the phase difference ranges from －14° to 29° and power ratio ranges from 0.7 to 1.4; when the angle between 1/2 wave plate fast axis and y axis varies from 35 °to 55°, the power ratio ranges from 0.47 to 2.1. The positions of 1/2 wave plate fast axis and 1/4 wave plate fast axis were solved by the second method when I/Q phase difference is respectively 80°, 85°, 90°, 85° and 100 ° and the I/Q power ratio is 0.5, 0.75, 1, 1.5 and 2. Either of this two methods can set the phase difference and power ratio simply and precisely，which is advantageous to the phase locking of the optical phase-locked loop and the enhancement of the intensity of the demodulated signal.