Microplastics (MPs) colonized by pathogens pose significant risks to the environment and health of animals and humans, however, the strategies for pathogens colonization in MPs and the effects of its colonization on spread of pathogens have not been fully characterized. Here, we investigated the biofilm formation mechanism regulated by c-di-GMP in Hafnia paralvei Z11, and determined the effect of MPs colonized by H. paralvei Z11 on the spread of strain Z11. Overexpression of yhjH, a c-di-GMP phosphodiesterase gene, attenuated intracellular c-di-GMP level in strain Z11, leading to an increase in biofilm dispersal and a decrease in biofilm formation. Meanwhile, the decline of c-di-GMP inhibited the expression of cAMP phosphodiesterase genes, increasing the cAMP content and promoting bacterial motility, that was responsible for the increase of biofilm dispersal. Furthermore, the formation of biofilms by strain Z11 on MPs promotes its colonization, which contributes to its vertical and horizontal spread in water after colonizing polyvinyl chloride-MPs and polypropylene-MPs, respectively. Therefore, this study reveals, for the first time, MPs colonized by H. paralvei Z11 through biofilms regulated by crosstalk between c-di GMP and cAMP promote the spread of strain Z11 in water, which expands the understanding of colonization strategy of pathogens on MPs and its risk on spread of pathogens.