Abstract: The Ling-long instrument is an astronomical instrument created by GUO Shou-jing, the famous Chi-nese astronomer fromYuan dynasty,in order to determine the astronomical data he needed to write the ＂Shou-shi calendar＂. There is a wide spectrum of opinions on the Ling-long instrument because there is no real model or blueprint left, and there is little related historical record or description on it too. Scholars from all over the world have various ideas about what kind of instrument the Ling-long really is, among them the armillary theory and the sphereplanetarium theory are the major two. In recent years more people are inclined to agree with -the sphereplanetarium theory, believe that the Ling-long is an imitating sphereplanetarium used in representing shows. Some manufacturers were even ready to produce Ling-long as asphereplanetarium. The author here questioned these two main theories about Ling- long in this essay, and put forward a new suggestion that the Ling-long is actually an astronomical instrument invented by GUO Shou-jing, different with armillary, sphereplanetarium, or any other instrument known by people.

Key words: GUO Shou-jing, Shou-shi calendar, armillary, sphereplanetarium, winter solstice point, Ling- long instrument