Through analyzing the problems existing in simulating root growth under external effect, regarding the feature that external effect can be decomposed into single impact factor (SIF), the root-soil system domain knowledge constructing method has been raised based on relational analysis of SIF. This method is based on external effects model database, mines the SIF data and builds Links among them, adopts multidimensional association rule of Apriori algorithm and threshold selection to select effective SIF, uses MATLAB to quantize data, and then constructs a domain knowledge database of SIF's effects to root growth, ultimately, uses OpenAlea and combines a root growth model to achieve the visuaLized simulation of root growth. Take soil compaction as an external effect to carry on a comparison experiment, the result shows that this method can prompt to complete a visuaLized simulation of root growth efficiently.