The walnut husk extract was prepared by hydroalcoholic method. The results showed that the antioxidant activity and total phenol content of the extract were 25 μg/ml and 175 mg/g, respectively. The minimum inhibitory concentration and minimum bactericidal concentration were determined in the range of 10 to 32 and 20 mg/ml, and the diameter of the zone of inhibition was determined as 2 to 7 mm. Then, low-density polyethylene/thermoplastic starch films containing the extract (1, 2, 3, and 4 wt%) were prepared. The results showed that the films containing 4 wt% extract (33.8 mm) showed the highest zone of inhibition.To investigate the morphological, mechanical and biodegradability properties, 4% by weight extract and tartaric acid (1.5 and 3% by weight) were used in low density polyethylene/thermoplastic starch films by extrusion/pressing technique. The studies showed that the mechanical and morphological properties of the composite films were improved by adding tartaric acid and extract. Then, biodegradability test (within 2 months) was performed on these samples and a plant container sample prepared from a domestic production unit with brand A claiming degradability.The plant container was made based on starch. In the low-density polyethylene/thermoplastic starch sample, the biodegradability percentage was 10.98 ± 0.01. By adding tartaric acid from 1.5 to 3 wt%, the biodegradability percentage increased significantly from 18.09 ± 0.03 to 25.24 ± 0.04. The presence of thermoplastic starch or thermoplastic starch-tartaric acid-extract in the polymer led to an acceleration in the reduction of molecular weight. On the other hand, the domestically produced plant container sample (Brand A) had the lowest degradation and biodegradability (5.14 ± 0.01) compared to the other samples. Therefore, the film containing 3 wt% tartaric acid and the film containing tartaric acid/extract had improved morphological, mechanical and biodegradability properties.