The antenna design of ground penetrating radar, partition radar and human contact microwave treatment equipment should consider the application scenarios and join the application scenarios together to design or simulate the calculation, so as to obtain the best application effect. In this paper, a circularly polarized dielectric antenna for contact microwave detection system is designed under the application background. The antenna operates at L band and is fed by stripline slot coupling. Circular polarization is achieved by unequal length cross coupling slits. The influence of the radiation background on the return loss, axial ratio and direction of the antenna is studied. The bandwidth of the object and VSWR<2 is simulated. The simulation result is 16.6%, and the measured result is 29.7%.