For traditional velocity detection method like superposition state vortex beam detection and vortex beam homodyne detection, the optical attenuation of the signal caused by long-distance transmission and light divergence would lead to that the detection system can not extract the signal accurately. However, the balanced detection based on vortex beam can solve this problem. But there is little analysis about accuracy and signal-to-noise ratio (SNR) of this detection system, which limits the engineering development of the detection system to a certain extent. Firstly, the homodyne detection was set as comparative item. By analyzing the accuracy change condition of balanced detection and homodyne detection based on vortex beam under different rotational velocity, it was verified that both of them can measure accurately. Secondly, it could be found that the balanced detection had significant advantage when signal light power was low by comparing the SNR of both with different signal light power. Finally, the relation of SNR of the balanced detection and local-oscillator power was revealed by analyzing the effect of SNR on different local-oscillator powers. And the cause of SNR changing with local-oscillator power was clarified.