With the development of science and technology, laptop becomes very popular. Laptop manufacturing firms are concerning how much spare parts they shall prepare to meet the demand of repairing. The quantities of spare parts are not only related to laptop life time, but also concern with users' repair willingness. We propose an approach to calculate the repair probability of laptop parts combined Poisson Process with users' repair willingness. In this study, the users' repair willingness relates laptop parts failure frequency. The new approach's verification is carried on by simulation. The significant test results show that simulation data fit theoretical value very well. By survey data and simulation result, we find that after four times broken for a laptop, a user will give up repairing it. The calculation result of new approach shows that spare parts quantities are entirely lower than traditional theory. From this point, if laptop manufacturers know their each parts lifetime, with the help of this paper, they can cut down their spare parts and save their service costs reasonable than before.