The invention discloses lactococcus garviea, a biological preservative and applications of lactococcus garviea and the biological preservative. Lactococcus garviea is named lactococcus garviea SY-1, with collection number of CGMCC No.9485. The biological preservative contains the fermentation liquor of lactococcus garviea. The fermentation liquor of lactococcus garviea SY-1 has stronger antibacterial and bacteriostatic activities, in particular, by being mixed and synergistically used with a Jerusalem artichoke leaf extract according to a certain proportion, the fermentation liquor of lactococcus garviea SY-1 has better control effects on black spot of root crops, such as Chinese yam, has the effects of greatly reducing the incidence of black spot and lengthening the storage time of the root crops and also has certain preservation effects. A mixture of the fermentation liquor of lactococcus garviea SY-1 and the Jerusalem artichoke leaf extract has numerous advantages, such as safety, high efficiency, non-toxicity, no residues and edibility, and has better economic and social values.