Abstract: With the development of science and technology, the demands of Internet of vehicle (IoV) and 6G for the fusion of communications and radar (RadCom) technology is gradually increasing. Orthogonal frequency division multiplexing (OFDM) RadCom systems based on sharing continuous-wave have two range processing methods: one based on the periodic autocorrelation function (PACF) and the other based on the frequency domain element level division. In range processing, these two methods have different effects on the received noise, resulting in the difference of radar performance. By analyzing the equivalent noise amplitude amplification factor and relevant sidelobe based on PACF and frequency domain element level division, this paper introduces the calculation method of critical signal-to-noise ratio (SNR) of these two range processing methods. Finally, the effectiveness of the proposed critical SNR calculation method is verified by the simulation evaluation of radar detection performance in the IoV scenario.