Currently, the standard IEEE 1012 is widely applied in the verification and validation (V&V) work for safety-level platform software in nuclear instrumentation and control systems. Based on this standard, V&V activities are sequentially conducted at the concept phase, requirements phase, design phase, implementation phase, and testing phase during the development of safety-level platform software. This paper focuses on research related to hazard analysis in the concept phase V&V and testing activities in the testing phase V&V. By further refining the requirements of the standard and identifying hazards through hazard analysis in the concept phase V&V, these hazards are further tested in the testing phase V&V. Additionally, by establishing a combined scheme for these two activities, test results are fed back into the concept phase V&V confirmation, forming a closed-loop quality control process. This approach enhances the completeness of V&V for safety-level platform software and has been practically applied in the development and testing of the VVER safety-level project’s CIS-V system, achieving good results. It provides valuable references for similar work in future projects.