Primary school students' thinking level is not high, so they need to be constantly cultivated in specific mathematics learning activities. The teaching unit of mathematical calculation is taught safely, stably and in small steps according to the inherent course. The knowledge they have learned is dribs and drabs, and there is no complete knowledge structure, and there is no connection between knowledge. The small space for students to explore is not conducive to students' independent migration and construction, and students' computing ability can not be fully cultivated. Therefore, it is necessary to conduct structured learning. Therefore, the whole structured teaching of units is a good attempt.