The ownership of the projects has transferred from the contractors to the originators in the repurchase period of the BT mode.In order to guarantee the success of transfer of the projects, it is extraordinarily important for the originators to control the risk of repurchase with effect.Taking mechanism as the cut-point, from the analytical perspective of the originators, this paper recognizes and analyzes the risks that may appear in the period of repurchase in BT projects, and structure a new risk management mechanism that suit the originator by reforming the process of risk management, the organization of management and the structure of mechanism.

This paper analyses the mechanism of extra earning by which the contractors make unbalance bid by utilizing engineering change, reaches two key nodes, and describes the process of engineering change with the help of the idea of triggering.On the basis of these, it constructs a FSD model which contains the forecast of engineering change, the simulation of the appearance of the expected engineering change and the design of the Bidding strategy.This model can be used as theoretical basic and provide contractors a standardized operation process of unbalanced bid.