Abstract: In order to evaluate the effectiveness of licensee oversight and quality assurance efforts associated with construction activities, the method of Construction Significance Determination Process (CSDP) was developed based on risk-informed approach and technology. The CSDP evaluation model for the VVER-1200 reactor and application process were established, which have been applied during the construction supervision for the VVER-1200 nuclear power plants. The application was carried out for two typical cases. The results showed that quantitative evaluation for abnormal matters can be achieved, and CSDP can help regulators focus on the most critical areas for safety, so as to optimize regulatory resources and improve regulatory efficiency.