Abstract: The modification of wheat gluten with L-cysteine was studied to improve the properties of wheat-gluten-based bioplastics, and its effect on the properties of the resulting bioplastic panels was discussed in terms of the amount of L-cysteine, processing temperature and processing time. The optimal process conditions for the bioplastic panels were obtained from orthogonal experiments. The results indicated that the optimal modification condition was determined as an L-cysteine content of 6 wt %, a processing temperature of 40 ℃ and processing time of 50 min. The bioplastic panels obtained under this condition achieved the tensile strength of 37.68 MPa, elongation at break of 22.83 % and water absorption of 76.08 % when the tensile strength was considered as a main factor. However, if the elongation at break was taken as a main evaluation indicator, the optimum modification condition should be determined as an L-cysteine content of 4 wt %, a processing temperature of 30 ℃ and processing time of 30 min. The bioplastic panels obtained under such a condition exhibited the tensile strength of 13.24 MPa, elongation at break of 80.19 % and water absorption of 80.31 %.