Expanding junior high school mathematics thinking ability is a long-term process, which requires students to accumulate and exercise constantly in the learning process. Here are some effective methods:

1. Cultivate logical thinking ability: Mathematics is a rigorous subject, which requires students to have strong logical thinking ability. Students' logical thinking ability can be exercised by solving some logical reasoning problems and proving problems.

2. Cultivate spatial imagination: Geometry and solid geometry in mathematics require students to have a certain spatial imagination. Students can improve their spatial imagination by drawing and making models.

3. Cultivate abstract thinking ability: The concepts and theorems in mathematics are abstract, which requires students to have strong abstract thinking ability. By solving some abstract problems and exploring mathematical laws, students' abstract thinking ability can be exercised.

4. Cultivate the ability to solve problems: Mathematics is a highly applied subject, which requires students to have strong ability to solve problems. By solving some practical problems and participating in math competitions, students' problem-solving ability can be exercised.

5. Cultivate innovative thinking ability: Mathematics is a developing subject, which requires students to have strong innovative thinking ability. By exploring new problems and putting forward new ideas, students' innovative thinking ability can be exercised.