The article addressed a number of primary school students’ difficulties when solving written math problems from the perspective of Psychology. Doing math exercises, especially solving written math problems, plays an important role in the intellectual development of primary students. Operations including writing out the problems from the words and the “knots” in thinking, coding the problems from words into specific mathematic solutions, and identifying the focus and the unit of the solution can be difficult. Understanding psychological difficulties in solving written math problems would contribute to completion for Maths learning in elementary education and establishing important bases for application to enhance effectiveness in teaching written math problems for primary school students.