Based on proportional difference theory, proportional difference characteristics of the cumulative distribution function of Weibull distribution were analyzed using proportion difference operator. On this basis, a new method proportional difference estimate method for direct estimation of the characteristic parameters of Weibull distribution is developed. Using this method, the characteristic parameters of either monomodal or multimodal distribution can be determined directly and accurately. Furthermore, this method can be applied to time-dependent dielectric breakdown research.