Abstract: Considering the nuclear effects on parton distribution,the energy loss of beam proton in initial state,and the finial state energy loss of c pair,the leading-order computations for J/ψ production cross-section ratios RW/Be(xF) have been explored and compared with the selected E866 experimental data with the J/ψ production occurring outside the nucleus, the obtained energy loss of the color octet is (0.69±0.23)GeV/fm.It has shown that with J/ψ production occurring outside the nucleus the energy loss of color octet in finial state plays a dominant role in the suppression of J/ψ production;in the larger xF range,the influence of beam proton energy loss effect in initial state can not be ignored.