The invention provides a device for measuring pulse carrier phase noise. The device is connected to a measured source and internally comprises a pulse adjustment unit, a phase discriminator, a pulse modulator and a reference source. The pulse adjustment unit couples and receives a measured signal through a coupler at the input end of the device for measuring the pulse carrier phase noise, and respectively couples and receives a measured signal and a reference signal through a coupler at the input end of the phase discriminator, pulse synchronous adjustment is carried out inside the pulse adjustment unit, the measured source and the reference source which are synchronized output an intermediate frequency signal after phase discriminating is carried out on the measured source and the reference source which are synchronized, after the signal is processed through a low pass filter, a PRF filter, a loop filter and the like, the reference source is adjusted to enable the reference source and the measured source to be orthogonally locked, and the phase noise of the measured source in the pulse modulation state is obtained through a low-noise amplification unit, an A/D sampling unit and an analysis and operation unit. According to the device, pulse synchronous adjustment can be automatically completed through an internal circuit, manual adjustment and manual intervention are avoided, and the setting process and the testing process are greatly simplified.