In this study, an interactive block-building system named as e-Block system is developed for children to learn the concepts of geometric structures and space. First, the system displays a picture (e.g., car or house) of the target object intended for the child to assemble. The child then follows the instructions provided by the system and uses various blocks to build the object. After the child has completed the task, the system employs a pattern recognition algorithm to automatically compare the assembled object with the picture and determine whether the shape is identical. The experimental results show that the proposed system achieves high accuracy rate, and children in testing are enjoy this system and have more motivation to play with building blocks.