The invention discloses a low-temperature biocontrol bacterial strain and an application thereof. The low-temperature biocontrol bacterial strain is Bacillus methylotrophicus WSWGH-10, is deposited with CGMCC and is assigned the accession number CGMCC No.11541 at Oct, 21st, 2015 and at the deposition address Chaoyang District of Beijing, Beichen road, Yard 1, No.3. The biocontrol bacterial strain can grow and reproduce at low temperature, can product various antibacterial substances, such as siderophore, chitinase, lipopeptides, proteins and the like, and also has the capability of degrading cellulose. The bacterial strain has a wide antibacterial spectrum, can inhibit phytophthora sojae, sclerotinia sclerotiorum, pathogen of maize stalk rot, fusarium moniforme, ustilaginoidea virens, rice wilt pathogens, potato rhizoctonia bacteria, root rot pathogen of acanthopanax, pathogen of cucumber fusarium wilt, botrytis cinerea and such pathogenic fungus and tobacco bacterial disease pseudomonas angulate holland and such pathogenic bacteria. The bacterial strain also has the function of promoting plant growth.