Doppler velocity is essential to analyze and forecast severe convective weather, especially mesocyclones and tornadoes Doppler weather radar is restricted by Doppler dilemma，ie, when the unambiguous velocity increase, the corresponding unambiguous range decreases, and even worse for the secondary or more trips echo appearTo alleviate Doppler dilemma, this article uses the random phase coding technique to recover second trip echoes to expand the velocity detection range based on the current volume scan mode of CINRAD/SA weather radarIt proved that the random phase encoding can recover the second trip echoes and remove third and more trip echoes It greatly improves the acquisition of velocity at low elevation and decreases the range ambiguous purple haze area caused by the limitation of velocity dealiasing algorithm without phase coding