Objective To evaluate the accuracy of three-dimensional (3D) reconstruction of the gallbladder volume based on computed tomography (CT) images and study the biomechanical changes in gallbladder motility to explore the relationship between gallbladder dynamics and gallstone formation. Methods A method for calculating gallbladder volume based on CT 3D reconstruction of The gallbladder model was proposed and compared with the ellipsoid method. A finite element model of the gallbladder was constructed for fluid dynamics analysis to simulate changes in gallbladder motor function under different angles of convergence between the cystic and common bile ducts and in the presence of gallstones. Results The mean errors of the specific gallbladder model volume and ellipsoid volume of the 50 patients were 7.26% and 25.35%, respectively. During the refilling period, the maximum pressure, deformation, and flow velocity of the pear-shaped gallbladder were significantly higher than those of the gourd-shaped gallbladder. The angle between the gallbladder and common bile duct had little effect on the bile flow pattern, and the maximum bile flow rate was reached at an angle of 120°. The bile flow velocity of the gallbladder with calculus was lower than that of the gallbladder without calculus, and there was a vortex near the calculus. Conclusions Calculating gallbladder volume based on CT 3D reconstruction is more accurate than the ellipsoid method. Compared with a pear-shaped gallbladder, a gourd-shaped gallbladder has lower gallbladder wall contraction, bile flow rate, and poor motor function. The bile flow rate in the gallbladder is slow, which is more likely to lead to the enlargement of gallstones or the formation of new gallstones.