By conducting adiabatic cyclic loading tests on three types of NiTi alloys with different martensite contents, dislocation densities, and grain size, the intrinsic influence mechanisms of different microstructures on the superelasticity, deformation modes, and elastocaloric cooling effect exhibited during the deformation process of NiTi alloys were studied. The results indicated that the presence of a large number of dislocations and martensite, as well as small grain size, can reduce the degree of superelastic functional degradation and the possibility of local uneven deformation in NiTi alloys. However, the elastocaloric cooling ability is weak, and the smaller the strain value, the better the superelasticity (minimum ε resin=0.23%), and the poorer the elastocaloric cooling ability (maximum ?T_cooling=1.7K). Completely eliminating dislocations and martensite, as well as increasing grain size, can achieve a significant elastocaloric cooling capacity (?T_cooling=25K), but its functional degradation phenomenon is severe (25K→9.6K, a decrease of 61.6%). By adjusting the dislocation and martensite content as well as grain size through the 400℃+15min annealing process, good superelasticity and uniform deformation ability can be obtained, as well as considerable elastocaloric cooling ability (?T_cooling=7.2K), and the degree of functional degradation can be improved. The current experimental findings provide valuable reference for optimizing the superelasticity and elastocaloric cooling effect of NiTi alloys.