In practice, most mechanical and electrical products life obeys Weibull distribution.This paper based on the relationship between Weibull distribution and exponential distribution, improved the point estimate of characteristic life during the normal stress and enhanced the precision of analysis. The point estimate of the shape parameter under normal stress level was presented, when the assumption that the shape parameter under different stress levels keeps invariable was got rid of. Meanwhile, a means was put forward to give interval estimation of the Weibull distribution parameter and the lower confidence limit of the reliability. Finally, an example of the mechanical and electrical product’s constant-stress accelerated life test was given and proved that the proposed approach is accuracy. It should be valuable for implement of engineering.