Abstract: Using the two-dimension reductive perturbgation method in this paper, the modified B-KdVequation of sheared magnetohydrodynamics in the comet-tail is derived and its nonlinear properties are investigated qualitatively. The primary results are: (1) Amodified B-KdVequation of sheared modified magnetohydrodynamice in comet-tail is derived; (2) The restrictive relations about macroscopic nonlinear wave acd sheared background in comet-tail are given; (3) The complicated structures in plasma comet-tail are explained qualitatively, and (4) Atransfer mechanism of interaction between solar wind and plasma in comet-tail is given.