Dynamic geometry technology has been extensively used in geometry education. To aid the teaching and learning of geometry reasoning, many efficient automated geometry reasoning algorithms have been integrated into the dynamic geometry system. However, the reasoning functionalities in most current dynamic geometry system cannot fully meet the requirement of the geometry reasoning education. To tap the educational potential of automated geometry reasoning to the maximum, we proposed the concept and implementation mechanism of constrained automated geometry reasoning in this paper, and developed a constrained automated geometry reasoning system with a convenient dynamic geometry interface. Experimental results show that the proposed system could successfully solve 107 out of 132 geometry proof problems, which means it can meet the basic requirement of the geometry education.