[Background] Potato dry rot is a fungal disease, caused by Fusarium spp., which always happens in both field and storage period. It mainly leads to quality deterioration and lower economic value. [Objective] To isolate and identify effective biocontrol strains to control potato dry rot, and investigate the inhibitory effect on plant pathogens. [Methods] We used 109 strains as tested strains, which were isolated from the rhizosphere soil of potato from Dingxi region in Gansu province. Antagonistic bacteria were screened by plate confrontation method with Fusarium sulphureum as the target strain, strain identification was based on morphology, physiological and biochemical characteristics and 16S rRNA gene sequence analysis. The effects of cell-free fermentation filtrate on the mycelial growth, spore germination of F. sulphureum, the lesion diameter of wounded inoculated potato tubers, the incidence of dry rot and germination of mung bean seeds were evaluated. [Results] Strain YL11 was isolated from the rhizosphere soil of potato and exhibited an excellent antagonistic activity against F. sulphureum, which was identified as Pseudomonas sp., cell-free fermentation filtrate of YL11 strain significantly inhibited the mycelial growth, spore germination of pathogenic fungi, the lesion diameter of wounded inoculated potato tubers and the incidence of dry rot. Moreover, the inhibition rate of 20% cell-free filtrate to F. sulphureum was 87.3%; 75% cell-free filtrate completely inhibited spore germination; the cell-free fermentation dip significantly reduced the lesion diameter of inoculated potato tuber, the inhibition rate was 67.1% after 14 days inoculation; the incidence of dry rot reduced by 68.4% after 90 days inoculation. Meanwhile, it also decreased the mycotoxin activity of F. sulphureum. [Conclusion] Strain YL11 significantly inhibited the growth of the F. sulphureum and had a notably biological control effect on potato dry rot, and it would be a potential biological control agent.