Abstract: The paper described the hemodynamics of blood flow based on fluid mechanics and its corresponding formulas, and revealed the limitation of blood flow velocity measurement for non-laminar flow when using the conventional pulse wave Doppler. The paper demonstrated the calculation of turbulence for blood flow based on velocity directions and quantified the turbulence according to the presented formulas. Two methods were introduced and the simulated results were analyzed. An example using real data based on ultrasound vector flow imaging for calculating the turbulence of blood flow was presented in the end.