The invention discloses a design method for a railway vehicle-mounted multi-band combined antenna. The method comprises the following steps: three kinds of three-frequency-band combined antennas are designed, wherein an A-type combined antenna comprises an LTE-R antenna, a GSM-R antenna, a GPS and a Beidou antenna, the B-type combined antenna comprises a 450 MHz antenna, a broadband antenna, a GPSand a Beidou antenna, and the C-type combined antenna comprises a GSM-R antenna, an LTE antenna, a GPS and a Beidou antenna; all the combined antennas are fixedly installed in roof space of a train,wherein two of the A-type combined antennas are simultaneously connected with ATP equipment, and the other three are respectively and independently connected with CRES equipment, CIR equipment and DMSequipment, the B-type combined antenna is connected with the CIR device and the DMS device at the same time, and one of the two C-shaped combined antennas is connected with the CRES equipment, and the other C-shaped combined antenna is simultaneously connected with the DMS equipment and the WTD equipment. According to the method, the problem that no extra space is provided for increasing more antennas under the condition that the current roof layout cannot be changed is solved, and all service devices are ensured not to be interfered and normally conduct data receiving and sending work.