The continuous circulation valve can maintain the circulation of drilling fluid when drilling is stopped， which can effectively solve the sediment at the bottom of the hole and the fluctuation of pressure at the bottom of the hole， especially for offshore oil and gas horizontal drilling. In this paper， a continuous circulation valve is designed， the structure and working principle of the continuous circulation valve are introduced， the force analysis and structural optimization design are conducted on the strength of the body under extreme working conditions， and the side opening of the bypass valve with a safety factor greater than 1.2 times was selected； A finite element stress analysis is conducted on the bypass valve， which comprehensively analyzes the stress distribution and sealing pressure. The influence of changes in the half cone angle of the sealing pair and the thickness of the valve on the stress and sealing effect of the bypass valve is obtained. The half cone angle of the sealing pair， α=30°， and the thickness of the valve core plate， δ=8mm， are optimized. and the bypass valve sealing test and body strength test are conducted， proving that the strength and sealing performance of the continuous circulation valve meet the actual usage requirements under the ultimate internal pressure of 35MPa and ultimate tensile force of 3503kN.