In order to improve the precision and efficiency of assembly manipulation in virtual assembly systems,first,a method to capture the assembly intention is proposed based on the constraint element-bounding box.Next,according to the feature parameters and fitting types of constraint elements,the pose transform is classifed into three cases： placing a point onto a line,placing a point onto a plane and being parallel a line to a line.Then,a precise positioning solving algorithm of constraints is proposed based on the pose transform of element decomposition.Moreover,the motion navigation for assembly is realized by solving the degree of freedom of the parts and mapping the motion component in the target constraint direction.Finally,a typical assembly case is studied to present the interactive aid process of assembly manipulation and demonstrate the effectiveness of the algorithm.The proposed algorithm has been successfully applied to the desktop virtual assembly system for aerospace products.