A method of data transmission between power electronic devices without a communication line involves generation of a digital signal in a data transmission process. The digital signal enables PWM modulation of specific data information via a composite modulation method. The composite modulation superimposes PWM modulation waves after modulating the PWM carrier frequency or conducting high-frequency modulation on the data. The composite modulation generates a PWM drive pulse signal which is transmitted to a power circuit via a main power electronic circuit to complete the data transmission process. In the data receiving process, signals are extracted on the voltage and current of a power line via software or hardware, and data demodulated to obtain the data information to complete the data receiving process.