People’s happiness is the ultimate destination of the Chinese Dream. Based on the macro data of each province, the evaluation standard of residents’ happiness index system is constructed by using entropy method, and the correlation test and PMG estimation are used to study whether trade opening can improve the happiness index of urban and rural residents in the short and long term. The results show that there is a strong correlation between the happiness index of urban and rural residents and the trade opening. In the short term, the trade opening can significantly improve the happiness index of residents, and has a stronger promotion effect on the happiness index of urban residents. In the long run, trade opening has an inhibitory effect on residents’ happiness index, and the weakening effect is stronger in rural areas. By region, trade opening has a stronger short-term promoting effect on the happiness index of urban residents in the central and western regions than that in the eastern regions, while it has a stronger long-term negative effect on the happiness index of rural residents in the central and western regions. In addition, the five dimensions of residents’ happiness index are not consistent with the short-term and long-term effects of trade opening, and there are great differences.