When the livestock is weighed dynamically, the EMD algorithm is selected for processing according to the non-stationary characteristics of the dynamic weighing signal. In order to solve the endpoint effect in the process of EMD decomposition signal, an improved EMD algorithm based on segmented envelope fitting endpoint effect is proposed. The algorithm first uses the least squares method to extend the endpoints, and then divides the envelope into the internal segments, extension points and extreme point segments, constructs the inner end of the extreme point by using cubic spline interpolation between the extreme points, and constructs the extension point and the extreme point segment by connecting the extreme point and the extension point according to the continuous condition of the second derivative. This effectively simulates the endpoint effect while reducing the error introduced by the extension endpoint. The experimental results show that the average relative error of the proposed algorithm is 0.21% and the maximum value is 0.33% after comparing the dynamic weighing signal of livestock processed by the proposed algorithm with the real weight data, indicating that the proposed algorithm has good accuracy and stability when applied to dynamic weighing.