Bidding stage is one of the important stages of cost control of project construction, which is a form of beforehand control and active control. In order to make rational use of construction funds and pursuit investment returns to a greater extent, the employer should strengthen the construction cost control in the bidding phase. To begin with, this paper analyzes the significance of construction cost control in the bidding phase, states the form of expression of construction cost in the bidding phase, and focuses on the analysis of influence factors of cost control in the bidding phase. Finally it puts forward some countermeasures to prevent the risk of project cost control in the bidding phase.