To reduce the material porosity in Laser Metal Deposition (LMD) processing, the Inconel 718 (IN718) was used as powder additive in this study, and the influences of main process parameters on the material porosity in a high deposition-rate LMD were investigated. Then, the methods to reduce the material porosity were researched by adjusting these process parameters. Based on the newly developed target with a high deposition rate by 2 kg/h in the LMD process, a coating experiment was performed by parameter solidification and parameter separation and the effects of laser power, scanning speed and powder mass flow on the material porosity were designed and carried out. Furthermore, the cross-sectional porosity and track porosity of tracks deposited by different process parameters were analyzed. The results show that as the laser power increases from 1 440 W to 4 214 W, the porosity of the longitudinal track decreases from about 1.5% to about 0.02%. When the scanning speed varies in the range of 500 mm/min to 5 000 mm/min, the range of track porosity is approx. 0.07% to 0.18%. Moreover, when the powder mass flow increases from 0.64 kg/h to 6.48 kg/h, the porosity increases from approx. 0.01% to 0.84%. It is shown that in high deposition-rate LMD, the scanning speed has no obvious influence on the porosity; and increasing laser power and reducing powder mass flow rate significantly reduce material porosity and increase the consistency of cross-sectional porosity.