The doping effect of Al3+ at B-site on the microstructure distortion of hexagonal YMnO3 was studied. The microstructures of the samples were determined from laboratory X-ray powder diffraction data and refined by the Rietveld method. The smaller ionic radius and different orbital occupation of Al3+ compared with those of Mn3+ decrease the lattice constants a and c, as well as the ratio of c/a. The tilting of MnO5 and the buckling were reduced, which were used to interpret the low ferroelectric transition temperature in YMn1-xAlO3. (C) 2010 Elsevier B.V. All rights reserved.