Due to the limitations of waveguide structure, chip packaging and other factors, the beam quality of diode lasers in fast axis is different from that in slow axis. Diode lasers are usually used as pumping source, i.e., luminance converter, and cannot directly act as a high-brightness laser source. We introduce an incoherent beam combining technology, called wavelength division multiplexing (WDM) beam combining technology, and it can improve the output optical power density and output beam quality of diode lasers. We summarize its development status and some important trends at home and abroad. The study provides a reference for the development of diode laser WDM beam combining technology.