Laser processing has become irresistible trend in the world. The demand for metal cutting and welding continues to grow and the laser source technology is designed to cope with different processing applications. This technology has evolved from carbon dioxide laser to fiber laser in the past. Currently researches have focused on exploring more efficient manufacturing methods to meet different processing applications. The fundamental technology for direct diode lasers (DDL) starts to develop gradually and advances quickly with time. The DDL system is to be designed with more than 40% of electro-optic efficiency and less than 4 mm.mrad beam characteristics. With its simple structure there is no need to use complicated fiber optic component fusion. It has been proved that the high-quality DDL laser system can process materials effectively. This study will introduce high-power laser processing technology from the past to the current generation of DDL.