The design of a novel magnetron injection gun with curved emitter for a W-band gyrotron traveling wave tube has been presented. An axial velocity spread of 1.84% with beam velocity of 1.1 is obtained by manual optimization. To overcome the complexity and inefficiency of manual optimization, numerical optimizing methods are employed. Optimizing codes based on genetic algorithm (GA) and simulated annealing algorithm (SAA) are completed by using the MATLAB program language. 2-D electro-optic code EGUN is employed to calculate and optimize the electron trajectories and beam parameters. The achieved velocity spreads optimized by GA and SAA are 0.81% and 1.05%, respectively, when velocity ratio is kept at 1.1. Compared with manual optimization, the numerical optimizing methods do not need the designers to get involved in the optimizing process. Besides, the numerical optimizing methods feature automation and high-efficiency, and often, the optimizing results are better.