From 7 to 10th century, the brick religion monument had been formed actively in Cambodia. The structure dating from same period of the time has been still remained but the succession of technique has been disconnected and this situation led to restore the ruins difficulty. This study focuses on the masonry construction technique among the ancient techniques used on Khmer ruins and determines what kinds of techniques were imposed. Furthermore, this study considers how each technique had been used and changed with the times. The object of investigation is the 36 of Khmer brick the structures were built from 7th to 10th century. According to the survey results, common technique had been used annually and the changed technique had been used by lapse of time. The common technique is called by 'the grid-masonry technique' that is the adhesive face would be rubbed each other and stick to construct and to use 'the completed brick' that is last member of framework. The other hands, we observed the changed techniques that make a height balance between floors and adapt a grade of wall horizontally with time. Then, we survey the masonry brick pattern and the ended technique with plaster mor