Modified Blalock-Taussig (mB-T) shunt is an effective palliative surgical method in the treatment of cyanotic congenital heart diseases. Although the surgical technique has improved over the years, it is still a challenge to control appropriate blood flow through the conduit. The formation of thrombosis in the conduit after the mB-T shunt may lead to severe desaturation or reoperation in some cases. Here, we applied the method of computational fluid dynamics (CFD) to study a patient-specific case based on medical images after the mB-T shunt. The real-time velocities derived from echocardiography and the pulsatile pressure waves measured during the operation were utilized as boundary conditions to physiologically capture the blood flow information in simulation. The calculated results were coincident with clinical measurements. Local pressure, blood flow distribution, streamlines, wall shear stress (WSS) and centrifugal force in the bended conduit were investigated. The results indicate that pressure decreases greatly through the conduit. The combined action of pulsatile pressure and WSS may lead to the damage of blood cells. The computational hemodynamics can be applied in future studies of establishing quantitative standards to evaluate surgical outcomes of the mB-T shunt.