The current mechanical pressure-holding ball valve is limited by the narrow space in the well， the pressure-holding ability is weak， the pressure-holding success rate is low， and the flexibility is poor. In view of the above problems， a design concept of a "semi-floating" coring and the pressure-maintaining ball valve is proposed. Based on the technical requirements of pressure-holding coring， numerical simulation and theoretical calculation are used to design and develop a "semi-floating" ball valve pressure-holding control technology. The innovatively designed "semi-floating" pressure-bearing structure changes the pressure-bearing position of the ball valve， effectively enhancing the ball valve pressure capacity. A new pneumatic control method is proposed， and the opening and closing of the ball valve can be controlled， which can effectively solve the problem of closing the ball valve in the operation of highly deviated wells and horizontal wells. The finite element comparative analysis of the "semi-floating" and fixed ball valve bodies and valve seats were carried out， respectively. The pressure-bearing capacity of the "semi-floating" ball valve reaches 70 MPa， and the pressure-holding capacity is significantly improved. The torque and minimum gas pressure of the ball valve are determined by theoretical calculation. The research results can provide certain technical support for the development of pressure-holding coring technology.