Objectives: To evaluate the role of exogenous interleukin-9 (IL-9) in the growth, proliferation and activity of interstitial cells of Cajal (ICCs) cultured in vitro, and to assess its role in maintaining the functions of ICCs. Methods: ICCs of murine gastric antrum were isolated and cultured in vitro. ICCs were identified with c-Kit and ANO1 immunofluorescent antibodies. Both fluorescence microscope and confocal microscopy were used to observe the effects of IL-9 on the growth, proliferation and activity of ICCs in cultured in vitro. ICCs were loaded with fluorescence probe Fluo-3/AM and the fluorescence of intracellular calcium concentration ([Ca²⁺]_i) was measured by confocal microscopy. The effects of exogenous IL-9 on the sulfated cholecystokinin octapeptide (CCK-8S)-evoked [Ca²⁺]_i elevation were observed by confocal microscopy. Results: Immunofluorescence results confirmed the successful separation and culture of ICCs in vitro. IL-9 in concentrations ranging from 0.02 to 1 μg/ml promoted the growth, proliferation and activity of ICCs in culture, and ICCs grew best with 0.5 mg/ml of IL-9. The presence of IL-9 could significantly increase the CCK-8S-evoked [Ca²⁺]_i oscillation, which is probably caused by facilitating the maintenance of the functions of ICCs under suitable conditions for culture. Conclusion: IL-9 could promote the growth, proliferation and activity of ICCs, reinforce the CCK-8S-induced [Ca²⁺]_i increment in ICCs, and facilitate the maintenance of the functions of ICCs under suitable culture condition.