Evolution of co-pyrolysis char structure significantly influences its reaction reactivity. To explore the effect of structure on gasification characteristics of char, two ranks of coal, including anthracite coal (AC) and bituminous coal (BC) were introduced to the pyrolysis of wheat straw (WS). Microlithic and pore textures of char were examined by X-ray diffraction and specific surface area analyzer. Based on fractal theory and deconvolution method, quantitatively analysis from the effect of WS on co-pyrolysis char structure was obtained. Kinetic parameters of gasification were solved via the non-isothermal method and thermogravimetric analysis under CO2 atmosphere. The results showed that WS promoted the specific surface area of both BCWS char and ACWS char, but the promotion on the pore structure, including average pore size, was different. WS inhibited the ordering and uniformity of micro-scale structure of BCWS and ACWS char. Positive synergy from kinetic parameters during gasification of co-pyrolysis char was observed. Exponential relationship from microcrystalline structure parameter and gasification reactivity was found.