Consumers initiating returns online may produce secondary packaging, while most of the packages are produced by plastics. The more products are returned, the more plastics are used. Existing research indicates that the plastic packages can contribute to the micro-plastics pollution of the environment. As consumer environmental awareness (CEA) improves, more and more consumers are willing to pay extra fees to change the materials of packages from plastics to others in order to protect the environment, prompting enterprises to adjust to their return policies. In this context, this paper takes environmental quality improvement effort and the environmental coefficient as decision variables, and compares the manufacturer’s optimal decisions under with and without return policy. Our results show as follows: (1) There is a positive correlation between CEA and environmental quality improvement effort and the environmental coefficient; that is, environmental quality improvement effort and the environmental coefficient increase with an increase in CEA; (2) When CEA is high (k≤τ≤d), there is a threshold for manufacturers to invest in environmental effort. However, when CEA is low (0≤τ≤k), regardless of the return policy the manufacturer implements, its profit increases with the promotion of CEA, and when the manufacturer allows consumer returns, the relationship is more obvious; (3) The manufacturer should adopt an appropriate return policy according to the changes in CEA. When CEA is low (0≤τ≤k), the manufacturer should adopt a without return policy; when CEA is high (k≤τ≤d), the manufacturer should adopt a full refund (r=p) return policy, which is the optimal profit, and increase investment in environmental protection. From the above conclusions, we suggest that the government should increase the publicity of environmental protection, consumers should establish the awareness of green consumption, and enterprises should increase investment in environmental quality improvement to achieve sustainable development.