To solve the problem of nonlinear characteristics of spherical vessels, an immune single neuron PID controller (ISNPID) is proposed in this paper. The ISNPID controller combines the immune principle with single neuron PID, it can improve the learning rate and reduce the adjusting time of single neuron PID controller. The interim process of the spherical vessel system could also be optimized. Good control performance of nonlinear system could be realized according to the on-line self-adjusting gain by the ISNPID controller. Simulation result shows that ISNPID controller has strong adaptability and robustness. Efficiency and applicability of the ISNPID controller could be proved in practical application.