A twodimensional,radiation magnetohydrodynamics model is applied to the simu lation of Zpinch plasma sausage instability.Different implosion mechanisms in the cases of the existence and the nonexistence of instability are analyzed,an d the effects of various initial density perturbation levels on the x-ray power and energy are investigated.Numerical results show that x-ray energy output is not susceptive to sausage instabilities in a certain extent but x-ray power ve rsus time is evidently dependent on the instabilities.In addition,this paper als o studies the effects of numerical treatment of extreme low density in Zpinch simulations on numerical results.