Abstract: In the ultra-high frequency (UHF), L and S bands shared by radar and communication, the complex electromagnetic environment with overlapping time-frequency brings difficulties to the detection, sorting and identification of radar reconnaissance system. Specifically, when there are a variety of modulation forms of large time width, large bandwidth, low power and noise like low intercept probability (LPI) signals in the electromagnetic environment. These signals could come from LPI radar or communication systems using the same frequency band. Aiming at the objective situation of time-frequency overlapping electromagnetic environment, its development trend is analyzed, the overlap probability of multiple signals is analyzed quantitatively. It is concluded that radar reconnaissance system needs to be improved. Finally, combining the latest technology development abroad, preliminary study on the improvement direction of radar reconnaissance system is given.