A direct Monte-Carlo simulation method was developed to calculate neutron yield and spectrum in (α, n) reaction. It is based on continuous collision method, using stopping power computed by the program SRIM to simulate the moderation of α-particle and the ACE format of the nuclear data library JENDL/AN-2005 to calculate the neutron yield and spectrum in (α, n) reaction. Moreover, a (α, n)-simulator was developed based on the program NPTS. (α, n) neutron yields of light nuclides obtained in our simulations are consistent with experiments. In terms of (α, n) neutron spectrum, our results are in good agreement with experiments in the cases of B, F and O targets, while deviations are present in the cases of C, Al and Si.