Semi-crystalline polymers are widely used in manufacturing drivers and capacitors. The two opposite surfaces of semi-crystalline polymer are coated with flexible electrodes and are applied with voltage. Because of static electricity field, semi-crystalline polymer film thins down along the thickness direction while extends along the horizontal direction. Reduction of thickness will lead to a higher electric field, and the positive feedback system has been sustained. When the electric field reaches the critical breakdown of electric field of semi-crystalline polymers, electromechanical coupling system of semi-crystalline polymers becomes unstable. Based on the method on electromechanical instability of semi-crystalline polymers under non-linear field, we use exponential model with two material constants to analyze the electromechanical stability of semi-crystalline polymers. Then, we obtain the relationship among the true critical stress, the true critical electric field of different semi-crystalline polymers and stretching rate. The numerical results show that, when the material ratio C (K(2)= CK(1).K(1) and K(2) are the parameters determined by the experimental stress-strain relationship) of the two material constants increases, the true critical electric field and electromechanical stability of semi-crystalline polymers will decrease. In addition, when C = 0, our result coincides with previous results. It is proved that pre-stretching load can increase the critical breakdown voltage of the polymer. Our conclusions may provide the guidance in designing material and manufacturing semi-crystalline polymer. (C) 2011 Elsevier B.V. All rights reserved.