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Fast magnetosonic (MS) waves have been suggested to be able to effectively accelerate radiation belt electrons.We present gyro-averaged test-particle simulations to investigate counter-streaming interaction between MS wave and radiation belt electrons.It is found that an MS wave can significantly scatter counter-streaming electrons through a non-resonant process.The corresponding energy diffusion coefficients for counter-streaming interaction are always comparable to those for co-streaming interaction,independent of wave normal angle.The pitch-angle and cross diffusion coefficients of counter-streaming interaction are much smaller than those of co-streaming interaction for small normal angles,while they become comparable for large normal angles.Moreover,the bounce-averaged diffusion coefficients exhibit quite different distribution from those for co-streaming or counterstreaming alone in the pitch-angle-energy space.These results suggest that the non-resonant effect associated with counter-streaming interaction is indispensable for the acceleration processes driven by an MS wave.