The purpose of this study is to understand the influence of the social welfare system on the socially vulnerable population and the significance of Christian social welfare by exploring the pastoral ministry from the perspective of Calvin's social welfare. Firstly, the Christian social welfare must play a central role in churches according to Jesus' preaching on service (diakonia). Secondly, there is a change in the perception of church individualism. Individualism can be expressed in the form of the church's quantitative growth and its drive for growth. In consequence, they tend to neglect providing a service to socially vulnerable people. That is why a church's individualism must be constantly reformed and churches must respond to the voice that says "Let Church Be Church". Thirdly, churches must bring changes to their systems. Calvin pointed out the importance of the role of a deacon and divides those who provide socially vulnerable people with aid from those who take care of them. It is necessary to establish the theological foundation for the Christian social propely. In other words, the Christian social welfare must be implemented based on a clear theological basis and sincere faith. The declaration of God's kingdom by Jesus means not only individual salvation but also healing those who are sick and serving those who are vulneralble. It holds important lessons for Chistians today.