To address difficult operation and high safety risk of the time-consuming and labor-intensive cement slurry mixing during pumping the cementing plug, the jet suction type cement slurry mixing device is designed based on the jet suction principle. Based on the discrete particle method, the numerical simulation of the movement of dry cement powder in the injection funnel was carried out to optimize the injection funnel semi-apex angle and the installation height of the modulation switch plug to eliminate plugging. The field applications verified the performance of the device. The study results show that the flow pattern of the injection funnel flow is the main reason for the blockage of the injection funnel port. With the increase of the semi-apex angle of the injection funnel, the stagnant area of the dry cement powder increases, and the volume flow rate decreases. The preferable semi-apex angle is 45°. Modulation switch plug can change the flow pattern of dry cement powder from the funnel flow to the whole flow. With the increase of the installation height, the volume flow rate of the dry cement powder is gradually reduced, and the installation height is preferably 70 mm. The field application shows that the jet suction type cement slurry mixing device can save more than 50% of the cement slurry mixing time. The water and cement powder are evenly mixed without plugging, which greatly reduces the probability of operation accidents like “cementing drill pipe” and ensures safe and efficient operation.