Abstract: According to the reaction mechanism of laser beam, powder particles and melting pool during the laser cladding process, a mathematical model of powder utilization efficiency was formulated. A quantitive expression describing the relation between the powder injection angle and the contour parameters of laser cladding coating was obtained. Based on thermo-physical properties of Fe55 alloy powder and laser cladding process parameters, the powder utilization efficiency, cladding coating height and cross-section area were calculated by means of AutoCAD software. The results show that the powder utilization efficiency, and cladding coating height and cross-section area increase with the powder injection angle increasing, and theoretically calculated values are larger than the experimental values. Owing to powder burning and mechanical losing in the process of laser cladding, the powder utilization efficiency, and cladding coating height and cross-section area reach their maxima simultaneously with the variation of powder injection angle. The ideal powder injection angle is 60.