This paper explores the evolution of pore structure parameters during Zhundong coal and biomass ash sintering at 1473 K. Additionally, the influences of blending biomass ash with different proportions are determined. The pore parameters, including the porosity, diameter, number, and frequency of the equivalent diameter, were processed by reconstructing and processing three-dimensional (3D) data on the basis of X-ray computed microtomography (XCT). The maximum porosities for the cases of pure coal and mixture of 10% biomass and 50% biomass during sintering are determined to be 46.6, 42.6, and 24.0%, respectively, while the frequencies of small pores (<0.2 mm) in the coal ash samples are lower than those in the other cases. In addition, the mineralogical phase transformation during sintering is identified by X-ray diffraction analysis. The condensate in the pores mainly comprises NaCl, CaSO4, and KCl, which indicates that the volatilization of alkali metals and the formation and gasification of anhydrite occur throughout the sintering process.