Considering the growth of tumor cells modeled by an enzyme dynamic process under an immune surveillance,we studied in anti-tumor immunotherapy the single-variable growth dynamics of tumor cells subject to a multiplicative noise and an external therapy intervention simultaneously.The law of tumor growth of the above anti-tumor immunotherapy model was revealed through numerical simulaions to the relevant stochastic dynamic differential equation.Two simulative parameters of therapy,i.e.,therapy intensity and therapy duty-cycle,were introduced to characterize a treatment process similar to a tumor clinic therapy.There exists a critical therapy boundary which,in an exponent-decaying form,divides the parameter region of therapy into an invalid and a valid treatment zone,respectively.A greater critical therapy duty-cycle is necessary to achieve a valid treatment for a lower therapy intensity while the critical therapy intensity decreases accordingly with an enhancing immunity. primary clinic observation of the patients with the typical non-hodgekins lymphoma was carried out,and there appears a basic agreement between clinic observations and dynamic simulations.