To study the effect regularities of radar equipment under in-band continuous wave radiation and reveal the interference mechanism of in-band continuous wave on radar, a certain step-frequency radar was used as the test object to establish a test platform. We use the full-level irradiation method to carry out experimental research on the interference effect of radar. The in-band single-frequency electromagnetic radiation effect test results show that the radar under test has the effects of inaccurate ranging and suppressed target echo level due to the continuous wave radiation energy in the band. The ranging error radiated interference power varies irregularly, and the target echo level gradually decreases with the increase of the radiated power. The in-band single-frequency continuous wave radiation sensitivity test results show that the radar under test is very sensitive to the in-band electromagnetic radiation energy, and the minimum required radiation field strength of 0.32 V / m (at a frequency difference of ?0.1 GHz) is enough for causing effective interference to the equipment under test (EUT). After the radiation frequency difference exceeds ± 0.16 GHz, the critical interference field strength starts to increase sharply. The continuous wave electromagnetic radiation effect of the radar under test shows obvious frequency selection characteristics.