Three conserved quantities of non-paraxial nonlinear Helmholtz equation are driven in theory, which are corresponding to the conserved quantities of nonlinear Schdinger equation (power, Hamiltonian, momentum). Formally, these conserved quantities can be simplified as that of the paraxial model when the non-paraxial term is ignored. In addition, the difference between the non-paraxial nonlinear Helmholtz model and the paraxial nonlinear Helmholtz model by analyzing the variation characteristics of the conserved quantities with the change of parameters of optical spatial solitons is studied. Especially, it is found that the divergence results of the Hamiltonian and momentum of optical spatial solitons can be suppressed in the non-paraxial model when transverse speed increases in paraxial model.