The decision tree algorithm is one of the most essential artificial intelligence data mining models. It has good application prospects in data classification, analysis, effect evaluation, and rule prediction. Therefore, this paper introduced the application of a decision tree algorithm to the intelligent evaluation of English teaching effectiveness. The basic structure and flow of the decision tree algorithm were expounded. According to the needs of English teaching, the decision tree rules and evaluation criteria were discussed. Visualization technology would be a meaningful mode of graphical or logical visualization of the form to provide users with a reference. To improve the deficiency of the decision tree algorithm, an optimization scheme was proposed. After the simulation experiment, this research result was obtained. The decision tree algorithm could improve the design quality of English teaching and evaluate the quality and effect of decision-making.