The article discussed the issue of psychological readiness for older preschoolers (5-6 years old). Familiarization with numerical symbols is essential to help children become more confident and eager to learn more and develop mathematical capacity in primary education. The results collected from studies in Vietnam have shown that using games integrated mathematical content (the practice of recognizing numerical symbols) helped children quickly understand the lesson content to form numerical symbols, which could meet the mainstream activities by the age of older preschoolers. Thereby, this demonstrated the close relationship between Mathematics and Psychology in preparing school readiness psychology for preschoolers. In other words, from the preparation of psychological readiness for children to attend primary schools, it is necessary to consider the achievements of math education to conduct effective math education.