In this paper, the effects of gasification temperature and blending ratios on cogasification reactivity of food waste char with sawdust/Shenfu coal char were studied via a thermogravimetric analyzer. Moreover, the relationship between synergy and char physical-chemical structure evolution was further studied using scanning electron microscopy equipped with energy-dispersive X-ray analysis (SEM-EDS), N-2 absorption, and Fourier transform (FT) Raman techniques. The results revealed a significant synergetic effect between food waste and Shenfu coal. The synergetic effect always occurred at the mid-later reaction stage and was enhanced with the increase in carbon conversion. However, no synergy was found between food waste and sawdust. In the food waste-Shenfu cogasification process, ash present in food waste (rich in Ca) transferred to the surface of Shenfu char without blocking the pore structure of Shenfu char. Moreover, the FT-Raman analysis revealed that the food waste ash reacted with Shenfu char to form more active sites, resulting in increased gasification reactivity. No ash exchange was found during cogasification of food waste with sawdust.