Laser full-penetration welding of novel in situ TiB2 particulate reinforced ZL101 composites was studied using three different welding velocities synchronized with proper laser power. The optimal welding process parameters for laser full-penetration welding of in situ TiB2 reinforced ZL101 composites were suggested. The SEM results show that few pores and uniform particle distribution were obtained. TiB2 particles are intimately contacted with Al matrix according to the results of high-resolution TEM. There was no evidence of chemical reaction at the interface.