The work aims to design a SAW tag model with high consistency of echo energy to solve the problems that the echo energy of the reflectors at different positions in the SAW phase code tags is inconsistent, vulnerable to noise interference and incorrect in demodulation, thus reducing the error coding rate. Based on the coupled-mode theory and COMSOL finite element simulation software, the relationship between the thickness and width of the reflector film and the reflectivity was established. According to the optimal principle, the structure parameters of the reflectors were designed to reduce the insertion loss and improve the energy consistency of the SAW echo signal. The simulation results showed that when the thickness of the reflectors was 530 nm and the width was 0.23λ, the reflectivity of the reflectors was largest. For the tag with great consistency of echo energy obtained after optimization of reflector structure, the thickness of the four reflectors were 640 nm and the width were 0.245p, 0.27p, 0.32p and 0.46p respectively. The maximum error of echo was 2.02%. The phase information of the tag before and after the amplitude consistency adjustment of echo pulse was extracted by digital quadrature demodulation method. According to the results, the phase information of the tag could be correctly recovered after the amplitude consistency adjustment of echo pulse. The proposed SAW tag model can improve the anti-interference and coding capacity of the tag.