Two of Mr Salwai's ministers, Jotham Napat and Matai Seremaiah, were sacked last week, apparently because of fears about their growing strength within the coalition government.
Santo MP Hosea Nevu has been appointed the new agriculture minister and Christophe Emelee is the new infrastructure minister.
Don Ken has been handed the justice portfolio.
The move gives Mr Salwai the backing of 35 MPs, and gives him enough support to survive any opposition motion - unless there are defections.
Photo by Loop Vanuatu. Caption: Vanuatu Prime Minister Charlot Salwai