Abstract: Food security is the foundation of a nation, with its core being the guarantee of food production security. The intensification of global climate change, the frequent occurrence of extreme weather and climate events, coupled with the uncertainty of the external environment, pose severe challenges to China's food production. The technology of agricultural land film mulching is of vital importance to ensuring food security. Currently, the global demand for food is continuously increasing. To prevent and control the risk of microplastic pollution caused by residual agricultural film, this study aimed to clarify the substitution potential of straw fiber-based fully biodegradable mulch films in crop mulching cultivation. The research developed two new types of mulching materials using straw as raw material: nitrogen slow-release coated straw fiber mulch film (NSFM) and lignin-coated straw fiber mulch film (LSFM). A facility garlic cultivation experiment was conducted with traditional PBAT/PLA mulch film and no mulch (CK) as control groups. Using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy, the microstructure and morphological evolution of the mulch films during degradation were characterized. The study systematically analyzed their effects on the absorption of medium and trace elements, quality, and yield components of garlic plants, and comprehensively evaluated their economic benefits. The results showed that LSFM, NSFM, and PBAT/PLA mulch films all exhibited good degradability. Within 0-100 days of mulching, the degradation rate of LSFM was higher than that of NSFM and PBAT/PLA; from 100 to 120 days, the degradation rate of PBAT/PLA was significantly higher than that of NSFM, but there was no significant difference compared with LSFM, indicating that NSFM had better field durability. In terms of improving garlic quality, both NSFM and LSFM significantly promoted the absorption and accumulation of medium and trace elements such as Fe, Zn, and Se in plants. Among them, the Se content in garlic under NSFM mulching was 51.85% higher than that under PBAT/PLA mulching; both new mulch films significantly increased the alliin content in garlic sprouts, with better effects than PBAT/PLA and CK, and NSFM could significantly enhance the antioxidant capacity of garlic. In terms of yield, there was no significant difference between NSFM and PBAT/PLA treatments, but NSFM was superior in dry matter accumulation efficiency. Overall, NSFM can stably maintain garlic yield and significantly improve its nutritional quality and antioxidant activity. This mulch film, made from agricultural waste, has better degradation controllability and field applicability. It is a feasible technical path to realize the green substitution of traditional PBAT/PLA mulch films and promote low-carbon agricultural production. The straw fiber-based biodegradable film is a green, low-carbon and multi-functional new material, which combines environmental sustainability with production practicability. It has broad application prospects in the future green development of agriculture.