A novel TM₀₁ mode high power microwave phase shifter is proposed which is composed of two crossed circularly polarized TE₁₁ mode converter. The phase of the output microwave can be adjustable in a range of 0°~360°. The electromagnetic behaviors of the circularly polarized TE₁₁ mode converter and the phase shifter are simulated by the software CST. The results show that the output microwave can be adjustable in a range of 0°~360°at the frequency of 1.75GHz with the error is not more than 1 °, the transmission efficiency in this range is larger than 97%, and the power capacity is larger than 4.3GW.