Using the coupled mode theory, an analytical investigation of scattering of laser beam by an acoustohelicon wave and the consequent amplification of the scattered modes and the acoustohelicon wave is carried out in a longitudinally magnetized semiconductor of a noncentrosymmetric nature. We have assumed the origin of nonlinear interaction to be the second order optical susceptibility arising from the nonlinear induced current density. The numerical estimations are made forn‐InSb crystal at 77 K. The threshold pump electric fieldE0this found to decrease with increasing wave number and decreasing scattering angle. The nonlinear dispersion characteristics for a right hand circularly polarized mode become positive forE0<E0thand negative forE0≳E0th. The nature of a left hand circularly polarized mode is found to be just the reverse. The steady state gain constants for piezoelectric (gp), deformation (gd), and both cases (gb) are also obtained. The influence of the doping level on nonlinear dispersion characteristics and gain constants has also been considered.