The embodiments of the present invention relate to the technical field of wireless communications, and in particular, to a method, system and device for performing uplink transmission, which are used for solving the problems existing in the prior art that the spectrum efficiency and transmission efficiency are relatively low when the uplink transmission is performed in the case that the uplink transmission power is limited. The method of the embodiments of the present invention comprises: user equipment mapping complex symbol data obtained by modulation mapping to Q sub-frames, where Q is a positive integer; the user equipment modulating the complex symbol data mapped to each sub-frame, respectively, so as to generate sending signals corresponding to each sub-frame; and the user equipment sending the sending signals over the corresponding sub-frames. Since the embodiments of the present invention map the data in a data packet into a plurality of sub-frames for transmission, the total transmission power of the user equipment can be correctly received, thereby improving the spectrum efficiency and transmission efficiency when the uplink transmission is performed in the case that the uplink transmission power is limited.