To solve the technical problems of large lifting weight and difficulty to realize prefabrication and assembling of cantilevered bent caps， using the excellent mechanical properties of UHPC， a new type of semi-precast prestressed UHPC-S-NC non-demolition molded bent caps， with the use of groove-type combination structure made of UHPC， steel plate and steel section （S） as the permanent formwork， and the pouring of normal concrete （NC） after erection， were put into position. In order to study its crack resistance and stiffness and evaluate its safety， a 1∶2.5 large-scale scaled model was designed and loaded in the whole process in conjunction with the actual project， and key experimental datas such as the deformation characteristics of the test beams， the magnitude of the cracking and ultimate loads， and the pattern of crack development and distribution were obtained. The crack distribution and strain development law of the test beams were analyzed； considering the plastic stress-strain relationship of the NC material， the cracking moment calculation mode and calculation method of the structural UHPC layer and NC layer were proposed； and the bending capacity calculation mode of the combined structure was proposed based on the cross-section equilibrium condition， while the calculation mode of the structural shear capacity was explored based on the code. The results show that： the new type of bent cap structure has the characteristics of fast construction and a high degree of assembly； the calculation results of cracking bending moment are in good agreement with the test values； the new type of bent cap structure has sufficient load carrying capacity， and so it is suggested to use the equilibrium conditions and superposition method to evaluate the load carrying capacity of the structure， and the results are biased towards safety； some specific suggestions for the design and construction of the structure are put forward for the actual project. The research results can provide a reference for the application of semi-precast bent caps.