Background:
In the past three decades, previous researches showed that students had various misconceptions of Newton’s Third Law. The present study focused on students’ difficulties in identifying the third-law force pair in gravity interaction situations.

Materials and methods:
An instrument involving contexts with gravity and non-gravity associated interactions was designed and conducted among students in junior secondary school, senior high school and university.

Results:
The finding revealed that students in all grades did statistically worse in gravity interaction contexts and had general difficulties in distinguishing interaction forces and balanced forces. However, students improved their reasoning on third-law force pair with the increase of grade level irrespective of contexts. Special difficulties for junior secondary school students in understanding gravity interaction were also addressed.

Conclusions:
It is important to emphasize that the educational contexts of gravity interactions should be paid more attention to.