The present invention provides a data transmission method, apparatus, and system. The method includes: performing coding and modulation on data; mapping the modulated data onto M carriers, where M is an integer greater than 1, a carrier spacing of the M carriers is greater than or equal to a data rate, and the carrier spacing is a spacing between center frequencies of two carriers; performing spectrum spreading, scrambling, and precoding processing on data mapped onto each carrier; performing multi-carrier modulation on the spread, scrambled, and precoding processed data; and sending the multi-carrier modulated data to a receiving apparatus. According to the data transmission method, apparatus, and system provided by the present invention, a carrier frequency offset sensitivity problem may be resolved, thereby improving reliability of a communications system.