In order to solve the design and regulation problems of graded porous scaffolds, the triply periodic minimal surface (TPMS) that based on implicit function was taken as the pore unit for constructing the porous scaffolds. And the TPMS structure was controlled by selecting different types of TPMS and defining the distance function. The transition of different structures of TPMS was performed by the weight fusion method. And the dual contouring (DC) algorithm and octree algorithm were used to divide the solid model of the defect bone into hexahedral elements to determine the target assembly spatial. Through the coordinate transformation of the isoparametric element method, the pore units were mapped into the hexahedral elements to construct porous structure. Finally, a Boolean operation was used to obtain a bone scaffold model with porous structure. The examples showed that the gradient model of various irregular pores could be constructed, and the pore size, porosity, and specific surface area of porous scaffolds could be controlled by adjusting the deformation, distribution, volume of the hexahedral elements, and the structure of the TPMS pore units, which provides a feasible method for the design and regulation of heterogeneous porous scaffolds.