Incubation capacity is not only a key factor for survival and development of business incubators, but also an important manifestation of the high-quality development of them. Recognizing the influencing factors of the incubation ability and promoting it has become an important issue to be solved urgently. Four business incubators and 10 incubating companies were selected as the research object, apply grounded theory to explore the deep-seated factors that affect the incubation ability. It was found that incubation situation, synergy between business incubators and incubating enterprises, incubation network improvement, and management of incubating enterprise clusters had significant effects on incubation capability. But their ways and paths of affecting it are not consistent. Research conclusions provide analysis framework and thinking guidance for the follow-up research. It also provides suggestions for promoting the development of business incubators.