In this paper, the laser welding of the 630 precipitation hardening stainless steel with the 321 austenitic stainless steel was considered. The experiments were carried out with the pulsed Nd: YAG laser under various welding parameters. The effects of power of laser, voltage, duration of pulse, welding speed, beam diameter and frequency, on the weld volume are investigated. The results show that the weld volume increases with voltage and frequency. The weld volume decreases with welding speed and beam diameter. Moreover, the study shows two effects for the duration of pulse. Up to some value of duration of pulse, the weld volume increases. Exceeding, this limit reduces the weld volume. The optical and scanning electron microscopic tests were carried out. The results show that the martensitic structure is produced in the 630 stainless steel side and the austenitic stainless steel is produced in the 321 stainless steel side. The microhardness tests across the samples were carried out. The results show the maximum hardness is for the 630 stainless steel side and the minimum weld hardness is for the 321 stainless steel side. The high voltage may cause hot cracks in the 321 stainless steel side. The effects of gas flow rate on the microstructure were also considered.