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<i>Pseudomonas fluorescens (P. fluorescens)</i> and <i>Pseudomonas fragi (P. fragi)</i>, two kinds of psychrotrophic <i>Pseudomonas</i> species with pathogenicity, are likely to contaminate foods and cause diseases even in fairly cold environments, an outcome which should be suppressed. This paper investigates the antibacterial mechanisms of <i>Dellaglioa algida (D. algida)</i>, a new type of low-temperature-resistant <i>Lactobacillus</i>, on two such <i>Pseudomonas</i>. By the enzyme treatment approach, the antibacterial substance existing in the cell-free supernatant (CFS) of <i>D. algida</i> is preliminarily determined as organic acid or protein; then, its inhibition effects are assessed under various culture environments, including pH value, salinity, and culture time, where the best antibacterial performance is achieved at pH = 6.00, S = 0%, and culture time = 48 h. A series of experiments on biofilms indicate that <i>D. algida</i> is not only able to inhibit the generation or damage the integrality of the biofilm of the two mentioned <i>Pseudomonas</i>, but also can reduce the motility, including swarming and swimming, of <i>P. fragi</i> and restrain the swarming of <i>P. fluorescens</i>. The aformentioned developed antibacterial mechanisms show the possibility of using <i>D. algida</i> in applications as an inhibitor for psychrotrophic <i>Pseudomonas</i> in the food industry, by virtue of its strong suppression capability, especially in cold environments.