Aiming at the quality of wireless communication in EMUs, a dual-frequency monopole antenna is designed based on microstrip line and branch method to meet the vehicle-mounted requirements of high-speed train. The size of the antenna is 23mm×36mm×1.3mm, the maximum gain is 3.8dBi, its working frequency band is 2.28~2.64GHz and 5.47~6.15GHz, the relative bandwidth in the 2.4GHz and 5.8GHz frequency bands is 14.6% and 11.7%, covering the ISM frequency band . Taking the internal environment of the CRH380A EMUs as the research object, using the CST electromagnetic simulation software, the simulation model of the vehicle-mounted antenna layout inside the carriage is established. At the same time, compared the transmission effect in the train with the free space. The antenna transmission coefficient in each BSS is between -20 and -50 dB in the ISM frequency band, and the RSRP belongs to the optimal level I. The effectiveness of the designed antenna and the reliability of its layout are verified. The research results have a good reference value for the design of the on-board antenna of the EMUs and the layout of the in-vehicle antenna.