The invention relates to a bio-controlling bacterial strain AT31 for preventing and curing greenhouse vegetable root knot nematode disease and rice sheath blight disease, belonging to the technical field of plant protection. The bacterial strain AT31 is shaking cultured in PDA culture solution at 37 DEG C and 180rpm for 20-24 hours, then is subject to centrifugation at 6000rpm for 10min, a finished bactericide product thereof has a total viable bacteria concentration of 1*10<9>-1*10<10>cfu / ml, can be used by pouring at roots when transplanting vegetable seedlings after being diluted by 100 times, or be manufactured into microbial fertilizer to be used a week before the vegetable seedlings are transplanted, and has a prevention effect of 58-82% for root knot nematode disease of tomato, loofah, cucumber and other vegetables. The bactericide is diluted by 100 times to be used in spray treatment on rice stem base, has a prevention effect of 64.7% for rice sheath blight disease, and can increase the yield by 22.33%. And the bactericide can also cure vegetable bacterial wilt and epidemic diseases, and can improve soil hardening phenomenon.