The defects forming mechanism in the Laser Rapid Forming(LRF) process of titanium and titanium alloy was studied through microscopic analysis methods.The results showed that there were two kinds of defects,porosity and ill bonding in the laser multi-layer cladding.For the LRF titanium and titanium alloy,the porosity was spherical and randomly distributed in samples due to the low loose density of the powders,and the oxygen content wasn't the factor to influence the porosity rate.The ill bonding tended to be irregular shape and generally occurred between the layers and the line boundaries.The laser energy density,overlap and Z-increment ?Z were main process characteristic parameters to influence the ill bonding.