The main beam of the conventional lateral detection antenna is perpendicular to the radiation surface of the antenna, which will result in a high false detection rate of flight detection. Therefore, it is necessary to study the antenna with forward tilt detection function in order to improve the detection accuracy. Based on HFSS software, a slit antenna structure was designed. The input parameters of the design were in the frequency band 36.85-37.15 GHz, the isolation between transmitter and receiver was better than 50 dB, the forward inclination angle was 20°-24°, the side lobe suppression was more than -10 dB, the antenna length was less than 85 mm, the azimuth angle was more than 80°, and the horizontal angle was less than 11°, the gain was more than 11 dB. The test results show that the gain is 12 dB. Under the condition of 36.85-37.15 GHz, the azimuth angle is between 116°-134°, the pitch angle is between 8°-9°, the forward tilt angle is between 22°-24°, the side lobe suppression is ranged from -11.45 dB to -14.60 dB, and the beam direction is controllable. In the frequency range of 36.5-37.5 GHz, the standing wave ratio(SWR)is kept below 1.413, the isolation between transceiver and receiver is kept below -51-132, and the total antenna length is 83 mm. The test results are consistent with the design, which can meet the design requirements, and provide antenna technical support for the UAV′s lateral detector.