Objective:To analyze the curative effect of the modified sinus tarsi small incision and minimally invasive internal fixation in the treatment of Sander Ⅱand Ⅲ calcaneal fractures and its influence on inflammatory factors and immune function.Methods:From February 2018 to February 2020, 116 patients with Sander Ⅱand Ⅲ calcaneal fractures admitted to the First People′s Hospital of Linping District, Hangzhou City were prospectively selected and randomly divided into the control group and the observation group according to the digital table method. There were 58 cases in each group, the control group was treated with traditional lateral L-shaped incision internal fixation, and the observation group was treated with modified tarsal sinus small incision internal fixation and minimally invasive treatment. The clinical indicators, incision healing, postoperative complications, Bohler angle, Gissane angle, interleukin(IL)-1β, IL-6 , IL-22 and immunoglobulin (IgA, IgG, IgM) before and after surgery were compared between the two groups. The function of the hind foot and ankle were evaluated by American Foot and Ankle Society Ankle and Hindfoot Function Score (AOFAS) before and 6 months after surgery.Results:The operation time, intraoperative blood loss, hospital stay and fracture healing time in the observation group were lower than those in the control group: (61.08 ± 15.17) min vs. (85.82 ± 13.50) min, (27.51 ± 2.64) ml vs. (82.53 ± 3.81) ml, (7.14 ± 1.18) d vs. (10.76 ± 1.50) d, (46.44 ± 8.16) d vs.(52.28 ± 10.40) d, there were statistical differences ( P<0.05). The Bohler angle in the observation group at 3 months after the operation was greater than that in the control group: (26.46 ± 3.64)° vs. (24.55 ± 3.86)°; and Gissane angle was smaller than that in the control group: (113.73 ± 6.56)° vs. (117.09 ± 7.16)°, there were statistical differences ( P<0.05). The grade A healing rate in the observation group was higher than that in the control group: 89.66%(52/58) vs. 32.76%(19/58), χ2 = 39.54, P<0.05. The incidence of complications in the observation group was lower than that in the control group: 3.45%(2/58) vs. 20.69%(12/58), χ2 = 8.12, P<0.05. The levels of IL-1β, IL-6 and IL-22 in the observation group at 3 months after operation were lower than those in the control group, the levels of IgA, IgG and IgM in the observation group at 3 months after operation were higher than those in the control group, there were statistical differences ( P<0.05). Conclusions:The modified tarsal sinus small incision internal fixation and minimally invasive surgery have better curative effect in the treatment of Sander Ⅱ and Ⅲ calcaneal fractures. The function of the hind foot and ankle is restored.