Redistribution of interest is an important issue in the renegotiation of PPP model. Reasonable redistribution of interest can promote renegotiation and the whole PPP project. Based on the Rubinstein Bargaining Model, this paper establishes the interest redistribution model under the PPP model and solves the model. It concludes that improving the fairness and rationality of redistribution in the renegotiation by adjusting the discount factor and reducing the bid time,etc.