The scattering of lattice solitons by a mass interface is studied through the use of reductive perturbation method. In the lowest order approximation, the incident soliton and the reflected and transmitted waves propagate independently of each other and each of them is governed by the generalized Korteweg-de Vries equation. The boundary condition at the mass interface is the same as that for linear waves. Reflection and transmission of solitons through the interface are qualitatively discussed. The results are compared with those of the recent numerical experiments.