A numerical simulation was developed for particle trajectory in flow field and spheroidizing of silica particle in oxygen-acetylene flame spheroidization process. Gas flow field and silica particle behavior in oxygen-acetylene flame spheroidization process was simulated using a Computational Fluid Dynamics (CFD) package FLUENT. A model was proposed for optimizing spheroidization process of silica particle. Oxygen gas and acetylene gas were used as the continuous phase. Silica particle was used as the dispersed phase. The three-dimensional, steady and isothermal flow field was showed for illustrating the continuous phase and the dispersed phase. Conservation equations of mass and momentum for each phase were solved using the finite volume numerical technique. Various gas conditions were discussed systematically. The injected silica particle trajectories were simulated by using dispersed particle surface trajectory. The trajectories and spheroidizations of different size particles were analyzed. The results of numerical simulation reveal that the flame length was reasonable and overall temperature was highest when acetylene gas flow rate was 10 L . min(-1), oxygen gas flow rate was 20 L . min(-1) and powder carrying gas flow rate was 5 L . min(-1) and 40 pm silica particles were difficult to finish spheroidizing within 5 x 10(-4) s. The comparison shows that temperature distribution, velocity distribution, particle trajectories, and deformation which were predicted by simulation, were in good agreement with the corresponding experimental results. (C) 2015 Elsevier B.V. All rights reserved.