The work aims to design a new control method based on fuzzy PID to improve the control effect of self-adaptive constant tension under the limit condition. Firstly, the structural mechanical analysis model of the packaging film was established by parameter fitting analysis. The mechanical parameters of the packaging film were simulated by load-deflection curve fitting method. And then the analytical model of the structural parameters was obtained by combining the area-combined continuous estimation method. On this basis, the elastoplastic mechanical model was constructed under the action of ultimate rotational stiffness through mechanical evaluation and analysis of external loads. Then the bending stiffness softening model was obtained after the ultimate resistance analysis and the optimal evaluation of the yield mechanical parameters, and then the adaptive control optimization was realized based on the fuzzy PID control. The simulation results showed that the output stability of the self-adaptive constant tension was stronger and the parameter optimization ability was good. According to the experimental results, the above constant tension control method has good control effect.