“Code of valuation with bill quantity of construction works”(GB50500-2008)published in July 2008 proposes a new concept of “Bidding Control Price” instead of “base bid price”. This paper firstly introduces the calculation program of Bidding Control Price which is different from the calculation program of base bid price. The calculation method of material price risk changes greater and it is the focus of our discussion. Article probes into the impact of material price risk on project cost, applying Grey Forecasting Model to discuss a reasonable method of determining material price risk, which provides a new feasible solution to determine an appropriate cost of project. Article concludes with examples which show that different material price risks have great impact of project costs. This paper has some instructive significance for the calculation of project cost in new code.