Since the traditional anti-statistical algorithms in the inversion of refractivity from radar clutter （RFC） need too much calculation, a new physical algorithm （variation adjoint combined with the regularization method） is proposed instead. In the variation adjoint method, the tangent model, adjoint equations and accompanying boundary conditions, the solving expression of adjoint equations, and the mathematical functional expression of the gradient were derived respectively, and the problem of how to coordinate functional gradient of the complex equations is solved. In the regularization method, to take into account the characteristics of radar electromagnetic wave propagation, we choose a suitable regularization term to solve the inversion of the ill-posed problems. Finally, the implementation of the iterative inversion algorithm was derived.