Abstract In recent years, the development of environment‐friendly biodegradable and high‐performing polymer composite for production has attracted much attention, motivated by the need to reduce the amount of microplastics accumulating in the environment. In this study, the poly (butylene adipate‐co‐terephthalate) (PBAT) and sodium lignosulphonate (SL) composite films with different loading of SL are synthesized. The PBAT/SL composite films show great UV‐blocking capability and photostability. When the addition of SL reaches 10 wt%, the UV‐B blocking of the composite films (P/L10) can reach about 100%. However, the tensile strength of P/L10 is about 32% less than that of neat PBAT. The silane modified nano‐SiO 2 (m‐SiO 2 ) , as a nano‐filler, is well distributed into PBAT/SL composites, leading to improved tensile properties and the compatibility of PBAT with SL. The tensile strength of the P/L10/S2 (S2 denotes 2 wt% m‐SiO 2 ) is about 55% more than that of P/L10 and 5% more than that of neat PABT. It can be observed from SEM that a suitable content of m‐SiO 2 can improve the interfacial compatibility between PBAT and SL. This work provides innovative strategy for biodegradable PBAT/SL composites with remarkable UV‐blocking ability and tensile strength.