Prediction of residence time distribution (RTD) in the modular type screiv extruders has always been one of the most attractive subjects for predicting. In the present work an attempt was made to establish a method with functionality similar to additive rule for predicting RTD of the modular screw extruders with different configurations such as Buss Ko-Kneader Results predicted from this method, which was named as cluster model, were compared with the results predicted based on our previously reported trajectory method as well as experimental results. A reasonability good agreement was found between these results justified reliability of the cluster model for being used as a new approach to predict the RTD of the modular screiv extruders.