《20以内退位减法》是小学数学一年级下册的重要教学内容,常用的计算方法有“画图计数法”、“破十法”、“平十法”与“想加算减法”等。笔者以一年级刚入学儿童为样本,选择能力较强、一般、较弱共计34名学生为抽样检测对象,内容设置了两道情境题,关注计算的思维过程,周期为三个学期,对每个学生进行访谈记录。通过前后实验数据表明,发现解决问题的正确率较高,80%的学生至少用一种方 “Less than 20 abatement subtraction” is an important teaching content of the first grade of the first grade of primary school mathematics, commonly used calculation methods are “drawing counting method”, “broken ten method”, “flat ten method” and “want” Add Subtraction "and so on. The author of freshmen enrolled in first grade as a sample, the ability to choose a strong, general, weaker a total of 34 students for the sample test object, the content of the two set of situation questions, concerned about the computational thinking process, the cycle of three semesters, each Student interview records. Through the before and after the experimental data show that the correct rate found to solve the problem higher, 80% of students at least one kind of side