For large delay problems that exist in industrial process control we Put forward the Improved Model-free adaptive control algorithm. The advantage is that the model does not require the specific object ,the system can be controlled just by the output and input. In the improved algorithm by introducing a constraint entry of the rate of change of the output with large time-delay to reduce the impact of large delay on the system. Verify that the improved algorithm can control the delay system effectively by MATLAB and SMPT-1000 simulation in the system response speed and system stability.