Abstract: Through analyzing the characteristics of modular fixture,exact placement technology of element for modular fixture assembly design in VE is presented to address the limitations of the existing approaches such as low efficiency of constraint recognition and inconvenience of treatment.Firstly,function space based constraint recognition approach is proposed.Through catching assembly intent,this approach can recognize the assembly relationship between assembling element and assembled elements with high efficiency.Secondly,the constraint solving method is discussed.The method includes adjustment of the position and orientation of assembling element to satisfy the confirmed constraint and analysis of the constraint status by using constraint matrix based DOF representation and reduction.Finally,to guide the assembly operation of designer,movement navigation algorithm is discussed.The methods mentioned above have been applied in self-developed system named as MFVADS.