Based on the CGSS 2017 annual data, this paper uses the Alkire-Foster Multidimensional Poverty Measurement to compare and analyze the different poverty characteristics of Migrant Workers in cities and Native Farmers in the five dimensions of education, health, assets, security, and social integration. It is innovative to introduce psychological mechanism to explore the influence and mechanism of individual mental health on multidimensional poverty. The study found that: Compared with the native farmers, the multidimensional poverty problem of migrant workers in cities is more severe, and the degree of inequality among poor groups is more serious. Mental health is an important factor affecting the multidimensional poverty of migrant workers. Subjective initiative lies in mental health and it plays a part of intermediary role in the path of multidimensional poverty. Under the background of building a moderately prosperous society in an all-round way, psychological poverty alleviation will be more important and urgent. A normalized mental health poverty alleviation work mechanism will be established, which will shift from diversion and assistance to prevention in advance to increase the happiness and sense of acquisition of migrant workers.