Plastic wastes are ubiquitous in the offshore and oceans with an increasing quantity, and inevitably, microbial communities colonized the plastics to form biofilms, which have become dispersal vectors for antibiotic resistance genes (ARGs). This study focused on the impact of plastic properties including hardness, wettability, and zeta-potential on the biomass, prokaryotic and eukaryotic communities and ARGs in biofilms formed on specific plastics (polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET)) in an estuarine environment. The results showed that, in comparison to PP, more biomass characterized by more dry weight, chlorophyll a (Chl a) and total organic carbon (TOC) was found in biofilms formed on PE and PET, which may be related to their lower surface wettability. Proteobacteria were the dominant prokaryotic phyla, and they accounted for 53.06%, 81.90%, 37.06%, 76.25%, and 54.27% of the total sequences in biofilms on PE, PP, PET, water and sediment, respectively. Ascomycota were the predominant eukaryotic phyla in biofilms, water, and sediment, and their abundances were elevated in biofilms on PP, which accounted for 34.73%. The biofilms on PP had a higher relative abundance of ARGs (3.13) compared to those on PE (2.59) and PET (0.23). Furthermore, both the plastic-biofilm properties (e.g. dry weight, Chl a, and TOC) and microbial communities (e.g., Fungi and Proteobacteria) may be involved in regulating the abundance of ARGs. Moreover, mobile genetic elements (MGEs) were significantly correlated to both the absolute and relative abundance of ARGs, indicating that MGEs may regulate the migration of ARGs in biofilms. Taken together, this investigation provides the significance of the plastic type, surface properties, and surrounding environments in shaping microbial communities and ARGs in biofilms formed on plastics.