In order to evaluate the changes of water resources carrying capacity after co-governance on five water categories was put into effect, taking Linhai City as an example, 17 evaluation indices were selected to construct the evaluation index system of water resources carrying capacity, the method of principal component analysis was used to reduce the dimension of the evaluation index, and a multivariate linear regression model for corresponding driving factors of water resources carrying capacity was set up. Three principal components of water resources natural support capacity, level of social life, and economic development level were extracted, and the entropy value method was used to determine the weight of subsystem, calculate and analyze the composite scores of water resources carrying capacity. The results show that the water resources carrying capacity in Linhai City has an obviously increasing trend after the plan of co-governance on five water categories was carried out, and anti-polluting, seeking for new water supply, saving water consumption are the main factors of improving the water resources carrying capacity.