The generation of polyethylene mulch film (PEMF) has promoted the rapid development of agriculture, while the non-degradability of it has caused the serious damage for the ecological environment. Currently, the biodegradable mulch film is considered as the most promising green substitutes for petroleum-based PEMF, owing to its environmental friendliness and biodegradability. Hence, this study fabricated a biodegradable mulch film (PSGA) through the crosslink (the esterification/amidation reactions and hydrogen bonds) between polylactic acid waste liquid (PLAWL) and sodium alginate (SA)/gum arabic (GA). Then attapulgite (ATP) was added to improve the mechanical properties. Therein, PLAWL was a kind of waste liquid from the fabrication process of polylactic acid (PLA) based on straw. At the same time, PSGA had similar insulation and water retention performance to PEMF and great UV resistance, thermal stability, and hydrophilicity surface. Additionally, pot experiment showed that PSGA could significantly promote the growth of Chinese white cabbage and the degradability ratio of that could reach 50% in a month. The total amounts of Rhizobiaceae (Ensifer and Allorhizobium-Neorhizobium-Pararhizobium, fixing free nitrogen gas and providing nitrogen nutrients for plants) in soil with PSGA was 12%, which was obviously higher than that in blank (4.5%). Therefore, this study provides a high-value recycling route for industrial waste liquid, offering an alternative solution to PEMF.