A brief introduction is made to the characteristics, structure, and phase stability requirement of the low-phase noise Doppler weather radar transmitter, as well as the key technique problems in having transmitter meet the requirement of the pulse Doppler weather radar. To improve the phase noise, several technique used in the transmitter, including the full-solid modulator, flyback electrification, electrification verification, and synchronous AC square-wave steady-current power supply and so on. An analyzed are made of the main factors that influence the inspecting performance of the pulse Doppler weather radar and the side-band phase noise resulted from the effect of the autoeciousness modulator on the RF pulse signals. The analysis results indicate that the unneeded autoeciousness modulation and noise are produced by a series of sources, and the main factors influencing the phasic stability of the Doppler weather radar include RF-Driven sources, power-supply ripple waves, pulse time jitter, amplitude modulation, microphonic effect, electromagnet induction, electromagnetic interference radiation sources, etc. These unneeded side-band noises limit the sounding capability in clutter of theDopplerweather radar.