Geometry theorem proving involves skills that are difficult to learn. Instead of working with abstract and complicated representations, students might start with concrete, graphical representations. A proof tree is a graphical representation of a formal proof, with each node representing a proposition or given conditions. A computer-assisted learning environment called MR Geo is proposed to help students in learning to do theorem proving, with the help of multiple representations including problem description, static figure, dynamic geometry figure, formal proof and proof tree. Empirical results indicated that medium-achievement students enjoyed most in interacting with these representations and found them most helpful in learning geometry proofs while low-achievement students changed their attitudes of hating geometry theorem proving. (Contains 4 figures and 4 tables.)