Abstract: In this paper,dynamic processes in the solar atmosphere are studied numerically from a complete set of MHD equations.Dynamic evolution of nonlinear magnetic field is produced by the finite amplitude of the azimuthal magnetic field at the base of the flux tube of the solar atmosphere.It is assumed that the initial configuration of the magnetic field is a force-free and potential field,the magnetic field is disturbed at the base,the plasma is driven and a part of magnetic energy is transformed into the kinetic energy of the plasma.The compressed flow of the plasma has the features of fast MHD waves.The computation results give quantitatively the nonlinear evolution of strong magnetic fields.These results could apply to the explanation of coronal transients,surge,spray and eruptive prominence events in the solar atmosphere,and to the modelling of plasma behaviour in high-βstructure experiments in the laboratory as well.