Major engineering projects characterized by intensive technologies and high investment are becoming more complex with increasing risks in a global market. Because incorrect investment decision-making can cause great losses to investors, quantitative risk assessment is widely used in establishing the financial feasibility of projects. However, existing methods focus on the impact of uncertain parameters, such as income, on decision variables of investment, neglecting assessing the impact of risk events, such as the sales of products falling short of expectations. In the context of international engineering projects from a risk driver perspective, this paper presents an improved quantitative risk assessment model to help risk managers identify the direct relationships between specific risk events and decision variables of investment. Stress testing is also introduced to assess the negative impact of extreme risks. The new model is applied to an on-going international petrochemical project to demonstrate its use and validate its applicability and effectiveness.