Char combustion of biomass particles is a significant thermo-chemical conversion process. The char combustion process of biomass particles with gas temperature fluctuation is numerically investigated. Considering the non-spherical shape of biomass particles, a fully algebraic expression of burning enhancement factor is theoretically derived to modify the char combustion rate of ellipsoidal particles. Four solid biofuel samples (cynara, pinewood, willow, and cardoon) are chosen for the calculations. The instantaneous mass variations and char combustion rates of biomass particles are calculated under different particle sphericities. Different kinetic parameters of biomass samples lead to various effects of gas temperature fluctuation on char combustion. The gas temperature fluctuation generally enhances the char combustion rate. Increasing the fluctuation frequency of gas temperature has no effect on char combustion. Under the same particle surface area, the char combustion rate is enhanced with decreasing particle sphericity.