Very low pressure plasma spraying is the object of numerous interests for the past years. The numerical simulations and experiments revolted some difficulties such as no-uniform plasma jet that has a strong influence on the thermal and deposit efficiency and more over on the coating structure shows the necessity of plasma gun optimization. For the numeric simulation the models proposed by commercial software are not completely adequate due of the local thermal equilibrium approach. In this paper we compare the results obtained by numeric simulation and experiments data for a Laval nozzle extension.