The purpose of this study is to examine the teaching process with the integration of games which has been used in number and calculation instructions for fifth grade elementary school children with varying ability. The teaching models and game designs were modified according to viewpoints of students, parents and teachers. In this study, students were not only divided into basic and advanced groups based on their varying ability but also instructed separately. The researcher will adjust the difficulty level flexibly for the two groupings. The four teaching units were: multiplication and division, factor and multiple, four basic algorithms, and equivalent fractions. The researcher designs the mathematical games which are suitable for lessons with reference to prior research within the country and abroad. After carrying out the integration, the effects and improvements were examined through students¡¦ learning records, parents¡¦ questionnaires and interviews. The results indicated that game teaching can motivate students and have better effects on teaching students in accordance with their aptitude by ability grouping. There were several indicators of improving learning effects such as peers¡¦ mutual cooperation, clarifying mathematical concepts, be familiar with calculation and mathematical problem solving, the improvement of learning attitude, etc. The learning effects were gradually increasing in the process as well. Besides, students could timely offer their opinions for the improvement of game designs after the instruction. As to the parents, they considered that students improve calculating abilities and reduce fear in mathematics when there was an increase in learning motivation. Parents were having high satisfactions with the whole teaching models and observed obvious progress in students¡¦ achievements. To enhance the participation of students, game designs should avoid complex calculation and add in rules with more variations and probabilities. The consideration of low achievement students in integration of games, giving encouragement and reward system should work together at the right time to enhance participation. Besides, the impact of the labelling of ability grouping should be reduced to avoid negative viewpoints. Finally, the teaching surroundings with games integration not only improve students¡¦ learning attitude but also develop problem-solving ability and help to develop and upgrade their mathematical ability.