The Japanese government’s decision on April 13, 2021 to discharge nuclear wastewater from the Fukushima Daiichi Nuclear Power Plant into the sea has aroused widespread concern around the world. People in Japan, especially fishermen, have expressed strong opposition to this decision. In this paper, we discuss an evolutionary game considering the impact of participants’ emotions to explore the evolutionarily stable strategies of both the Japanese government and Japanese fishermen. The results show the following: i) For the sake of interest, no matter what mood the fishermen are in, the Japanese government will choose to discharge nuclear wastewater. ii) The emotions of players not only affect their own strategy choices but also affect the strategy choices of other players. The emotional changes of Japanese fishermen not only affect the changes of their own strategies but also change the evolutionary trajectory of the Japanese government. iii) When both parties are rational, the impact of each key parameter on the evolution results and trajectories of both parties is closely related to the interests of both parties. When the fishermen are pessimistic, the changes in each parameter will not change their willingness to choose the opposition strategy but will affect the change in the Japanese government’s initial willingness to choose the discharge strategy. When the fishermen are optimistic, the cost of nuclear wastewater treatment and financial subsidies will slow down the evolution speed of the Japanese government to choose to discharge and Japanese fishermen to accept discharge policy. This paper also puts forward policy implications for the Japanese government and suggestions for Japanese fishermen to provide necessary support for the government to formulate pollution control policies and the people to protect their own rights and interests.