We perform several coefficients to simulate our algorithm when α are 0.15, 0.45 and 0.75. The experiment results show that with the increasing of β, the value of dif increases at first but decreases latter, the maximum values of dif in the three figures increases when α gets larger because the known criminals get more suspicion score from p than before. As we consider 0.15 appropriate for α, dif reaches its maximum when β is about 0.25, so we select 0.25 for the value of β.