Aim at the control questions of more interference factors, time-variant and oversize time delay in the proportion control of hydrogen and nitrogen in synthesis ammonia production, a self-adaptive predictive PID control scheme based on RBF neural network theory is presented, using ahead predictive to overcome large delay, and PID arithmetic based on RBF network to adjust the parameter of controller on-line. Results of simulation experiment show that this method has quick system response, strong adaptability and better robustness, it will be has wide perspective and practicability for the proportion of hydrogen and nitrogen in synthesis ammonia production.