Abstract: Microplastics (MPs) pollution in agricultural ecosystems poses a potential environmental threat to food security. Biobased plastics are considered as an effective alternative to conventional plastics. To investigate the difference of biobased microplastics (BMPs) and conventional microplastics (CMPs) on crop growth, this study evaluated the impacts of low-density polyethylene (LDPE), starch-derived polylactic acid (PLA), and cellulose-derived polyurethane (BPU) at concentration of 1% and 2% on seed germination and seedling growth of winter wheat (Triticum aestivum). The results indicate that MPs decreased the wheat germination rate by 4.2%-49.3% and germination potential by 11.6%-65.2% compared to the control treatment (without MPs addition), with inhibitory efficacy following PLA > BPU > LDPE. Higher concentrations of MPs exhibited stronger toxic effects on seed germination. Compared with the CK treatment, 1% LDPE promoted wheat growth, whereas BMPs (PLA and BPU) reduced root length by 40.6%-68.7% and shoot height by 22.9%-72.0%. MPs reduced chlorophyll a and b contents of wheat seedlings, with BMPs showing greater restrict efficiency than CMPs. 2% BMPs treatments reduced the total root length, root tip density and root surface area, while 2% LDPE did not exhibit significant root inhibition. In conclusion, short-term exposure to BMPs may impose greater phytotoxicity than CMPs on wheat seed germination and seedling growth, with higher concentrations exerting stronger inhibitory effects.