The simultaneous transmission scheme of dual polarimetric radar(PR) is now paid more attentions,but there is a bigger error on differential reflectivity in this scheme.The paper studies the relations between the phase difference of dual transmission port and the error of differential reflectivity,and the infections of dual transmission power and receiver gain distinction to differential reflectivity.In terms of the necessary of rainfall measurements and hydrometeor discrimination,an improved method for simultaneous transmission is advanced based on the theory study,and the simultaneous signal processing scheme is provided.This new improved method can increase the ability of measurements and discrimination via reducing differential reflectivity error through changing phase between H and V channels.This scheme has many advantages including:(1) improving measurement quality by changing phase between H and V channels,(2) enhancing SNR and signal intensity of weak echo in spite of co-polar or cross-polar port,(3) obtaining elliptic depolarization ratio(EDR),(4) transmitting linear,circular or elliptic polarization at different elevations in one volume scan,and(5) eliminating ferrite switch and phase alternation for different elevations.Polarimetric radar development is a complicated,synthetic and scientific subject,every polarimetric scheme has some advantages and disadvantages,therefore the goal of this thesis is to consider the theory and technology of PR confronted in China.This improved method should be further examined and developed in practice.