A crystal-diffraction experiment is discussed to test weak equivalence principle for neutrons. The idea of the experiment is based on essential magnification of any external force, acting on a neutron under diffraction at the Bragg angles close to the π/2 for Laue diffraction case. The enhancement factor from diffraction for neutron trajectory "curvature" in the crystal due to an external field can reach magnitudes of about ∼ (10 8 - 109) in comparison with a "free" neutron in the same field. Hence, the accuracy to measure the ratio of inertial to gravitational neutron masses can reach ∼ 10-5, that is about one order higher than best result. © 2011 Published by Elsevier B.V.