The invention provides a PS mixture of compound biocontrol fungicide for preventing the soil-borne diseases of vegetables, belonging to the technical field of crop disease prevention and cure. The PS mixture consists of two biocontrol bacteria, namely PX35 and SM21 respectively. The PS mixture is prepared through the following steps: culturing the two bacteria by shaking at 180 rpm at the temperature of 37 DEG C in a PDA (potato dextrose agar) culture solution for 20 to 24 hours respectively; then, centrifugating at 4,000g for 10min; and preparing the PS mixture from humidin and thallus preservative fluid by a ratio of 1:40 and further evenly mixing by a ratio of 1:1, wherein, the total concentration of viable bacteria in the finished product is 1*10 to 1*10 cfu / ml. Under the greenhouse condition, the control effect of the PS mixture on the bacterial wilt of solanaceae crops is 67.40%, the control effect thereof on the plague of solanaceae crops is over 77%, the control effect thereof on vegetable root knot nematode is 58.59%, and the effect of growth promotion is obvious; under the field condition, the control effect is stable, the yield can be increased by 50% to 80%; and at the same time, the PS mixture can prevent the soil from hardening.