The invention belongs to the technical field of communication interference resistance, and relates to a position pattern design method for a pilot frequency pattern modulation system. The invention, based on the purpose of improving the error performance of the system, provides a pilot frequency pattern mapping optimization activated subcarrier position grouping method for an SIM-OFDM system. According to the method, when channel information is unknown, Euclidean distances between all possible transmitting symbols are measured to select out an index bit mapping set with the lowest error code probability, and corresponding sub-carriers are activated according to index bits during index modulation so as to improve the system performance.