There are many solutions to the direction finding problem of the radar radiation source on a single platform, but the high-speed and high-precision direction finding method needs further research. In order to obtain the accurate estimation value of the phase difference of the radar emitter and solve the signal arrival azimuth angle, this paper combines the theoretical ideas of the long and short baseline method and the virtual baseline method, and proposes a virtual ultra-short baseline phase interferometer defuzzification algorithm. Under the condition of poor signal-to-noise ratio, as the phase error increases, the correct rate of defuzzification can be maintained above 70%; the root mean square error of the azimuth angle can reach 0.05°. It is verified by simulation that the defuzzification algorithm used in this paper has high-precision characteristics, and has theoretical and practical significance for measuring the azimuth angle of the radar radiation source.