The "basic thought" of primary school mathematics mainly refers to deduction and induction, which should be the main line and the highest thought of the whole mathematics teaching. Deduction and induction are not contradictory, nor are their teaching. By summarizing the prediction results, the results are verified by deduction. In specific problems, it will involve mathematical ideas such as mathematical abstraction, mathematical model, equivalent substitution, combination of numbers and shapes, but the most important idea is deduction and induction. The reason why we use "basic thought" instead of basic thought method is to distinguish it from concrete mathematical methods such as method of substitution, recursive method and collocation method. Each specific method may be important, but they are all individual cases and are not universal. There is no need to master it as an idea. After a period of time, students are likely to forget it. The idea mentioned here is a big idea, which is the kind of thinking method that students hope to benefit for life after understanding it.