Abstract: The Cultivation of students’ critical thinking is an important job of mathematics teaching. Critical thinking in mathematics refers to the thinking process of perceiving and storing information, mental processing, obtaining new conclusions and improving feedback on a mathematical content. Critical thinking in mathematics has the characteristics of truth-seeking, critical questioning, logical argumentation and timeliness of feedbacks. The mental process of critical thinking includes the stages of information perception, mental processing, conclusion output, and feedback refinement. Among them, mental processing includes doubting, puzzling, questioning and inquiring and other mental activities. The monitoring of thinking is omnipresent during the whole process of critical thinking in mathematics. The psychological process of critical thinking has many implications for mathematics teaching: first, to improve the personality of critical thinking in mathematics; second, to stimulate students’ "three consciousnesses"; third, to improve students’ "three abilities"; fourth, to develop meta-critical thinking in mathematics.