Preferential tax is the main policy tools for the world to incentives its enterprise to increase its investment in the research and development, and it’s also the government to change its way of support and encouragement to the innovation of science and technology of the private enterprise. How to measure the incentive effect of the tax on the scientific and technological innovation of the private enterprise, the paper use the statistical analysis, hypothesis test and statistics data validation, etc to demonstrate that:Appropriately designed system exerts a positive and significant effect on R&D investment, which can effectively reduce the company's development costs and risks.