1 Tiananmen Square
The largest city square in the world, Tiananmen makes for a grand spot to fly a kite. Being THE tourist attraction of the capital, it's great for people watching as well. 天安门广场

2The Temple of Heaven
There are more open places in the Temple of Heaven than any other park in Beijing. The best of the best in kite flying gather here so go to show off or learn from the masters.
Tiantan Lu, Chongwen District 崇文区天坛路

3 China Millennium Altar Square
Right in front of the China Millennium Altar, the square is open enough for flying kites. On any given spring day, there are many, many kites in the sky over the CMA. Be careful around the power lines along the edges of the Square.
A9 Fuxing Lu, Haidian District 海淀区复兴路甲9号

4 Chaoyang Park
Chaoyang Park is the biggest park in Beijing. There are open areas where people fly the special Chinese two-handed kites. Just be careful of the trees.
1 Nongzhan Nanlu, Chaoyang Distrcit 朝阳区农展南路1号

5 Mangshan Mountain
Northeast of the Ming Tomb Reservoir (Shisanling Shuiku), Mangshan Mountain has a slight slope stretching out to the reservoir, which is perfect for camping and flying kites. With beautiful mountains on one side and water on another, this makes an ideal spot for getting away from the city. Enjoy the fresh air. Be careful though, some parts are rocky and steep.
Northeast of Ming Tomb Reservior (Shisanling Shuiku) 十三陵水库东北面