A method, an apparatus, and a system for coding and modulating data are disclosed. The method includes: obtaining, from a receiver and a transmitter, parameters for calculating power consumption of the transmitter; calculating, according to the parameters, the power consumption of the transmitter under various combinations of modulation orders and coding rates supported by the transmitter; and selecting a bitwidth, modulation order, and coding rate corresponding to minimum power consumption of the transmitter to code and modulate data sent to the receiver. The method, apparatus, and system provided in embodiments of the present application save power consumption of the transmitter, and greatly improve energy utilization of a wireless device having a digital processing unit.