Nowadays, the workers in automobile service enterprise use their experience to decide the using limiting clearance between crank pin and bearing bush. It is not enough to be scientific and accurate and it has caused waste on the manpower and financial resources. By using the theory of finite element and getting help from the large analysis software ANSYS, this paper calculated the limiting value of fit clearance between the crank pin and bearing bush scientifically which is in some engines belonged to the vehicle types of Volkswagen. Based on calculation, it has been found that the using limiting value of fit clearance between crank pin and bearing bush was generally small. The analysis and calculation in this paper has guiding significance to the development of automobile maintenance trade.