In this study， antagonistic yeast for controlling black spot of postharvest cherry tomato was to be screened by in vitro and in vivo test， and the biocontrol efficacy of this antagonistic yeast against the natural decay of cherry tomato and its effects on the quality of fruits were then investigated. The direct and indirect inhibition of this yeast on Alternaria alternata was explored through its effects on spore germination， germ tube elongation and hyphae structure of this pathogen， and its growth dynamics on wound and surface of cherry tomato， respectively. Then， the effects of antagonistic yeast on the expression levels of resistance-related genes in cherry tomato were determined by RT-qPCR technology to analyze the effect of antagonistic yeast on the disease resistance of the fruits. Results indicated that Pichia caribbica showed the best control efficacy against postharvest black spot of cherry tomato， and the disease incidence of yeast-treated fruits was only 16.25% which was significantly lower than that of the control (68.76%). This antagonistic yeast could also significantly reduce the natural decay of postharvest cherry tomato and slow down the deterioration of quality. P. caribbica could directly inhibit the growth of A. alternata by inhibiting the spore germination and mycelial elongation as well as parasitic on mycelia of A. alternata. It also could indirectly inhibit the growth of A. alternata by competing with the pathogen for nutrition and space on the wound and surface of cherry tomato. P. caribbica could induce the expression levels of antioxidant genes (SOD， CAT and APX) and pathogenesis-related genes (PR genes) (GLU and CHI) in cherry tomato. P. caribbica showed biocontrol efficacy against postharvest black spot and natural rot of cherry tomato， and had no significant adverse effects on fruit quality. It alleviated postharvest diseases of cherry tomato by inhibiting the growth of pathogen and increasing the expression of resistance-related genes.