The precursors (ZnSn(OH)(6)) of ZnSnO3 hierarchical microspheres have been synthesized by an facile chemical precipitation method at room temperature followed by self-assembly, and then, the precursors were converted into hierarchical ZnSnO3 microspheres composed of nanoparticles by annealing. The structure and morphologies of the products were characterized by a series of analysis methods. The sensing performance of the ZnSnO3 microspheres to formaldehyde was studied, and the sensing mechanism was also discussed in detail. The sensing tests indicate that doping Pd can significantly improve the sensing properties of ZnSnO3 to formaldehyde, especially when the doping proportion of Pd is 4wt%. In addition, the material has low detection limit of 100ppb and shows linear response to formaldehyde in the concentration range from 0.1 to 10ppm at operating temperature of 103 degrees C. All the above properties indicate that the 4wt% Pd-doped composite is an attractive sensing material for detection of formaldehyde.