Low-density foamed cement can address formation leakage issues during cement displacement. The mechanical method is the priority approach for on-site foamed cement slurry preparation, and foamed cement generator serves as the pivotal component, which determines the fast and efficient performance of foamed cement preparation. Based on CFD numerical simulation, the average density across the pipe section downstream of the foamed cement generator and the density variations along different axes in the flow direction were compared to assess the uniformity and efficiency of foamed cement preparation. The distribution of pressure field and flow field downstream of foamed cement generator were compared to evaluate pressure lose and turbulence intensity during multi-phase fluid mixing. The results indicate that lower injection pressure leads to a shorter mixing distance between gas and cement-based slurry and better mixing result. Higher foamed cement flow rates correspond to increased turbulence intensity in mixing gas and cement-based slurry, resulting in faster and more uniform mixing. The SK-static mixer is utilized downstream to enhance turbulence intensity of the flow field. Although this increased pressure loss to a certain extent, it significantly improved the uniformity of foamed cement mixing. Evaluating the slurry preparation performance of the foamed cement generator can guide optimal generator design and achieve efficient preparation of uniform and stable foamed cement with a high flow rate.