The invention discloses a disease-preventing, growth-promoting and stress-resisting bacillus amyloliquefaciens Y15 for all plants and an application of the bacillus amyloliquefaciens Y15. The bacillus amyloliquefaciens is a biocontrol bacterium Y15, which is preserved in China General Microbiological Culture Collection Center on November 22, 2016, with strain preservation number of CGMCC NO.13327. An inoculant, which is higher than 1*10<8>CFU/mL in concentration, can be prepared from the bacterium; under a room-temperature normal management condition, the bacillus amyloliquefaciens Y15 inoculant, applied to root irrigating treatment, can achieve a biocontrol effect, which is greater than 50%, on various plant diseases; the inoculant can achieve a growth-promoting effect, which is greater than 18%, on various crops; in fields, an effect of preventing and controlling various diseases is greater than 47.05%, showing a quite obvious growth-promoting effect; and in addition, the inoculant can significantly enhance stress resistance of the plants.