Abstract: For input information of project risk assessment is only limited to expert language information, the concepts of risk present value and risk trends are proposed to process the dynamic risk issue caused by uncertainty according to the time dimension. Time variable is introduced into project risk assessment, considering risk event expected time of occurrence, duration, and distribution. Dynamic risk ranking and risk trends are rationally assessed based on the time variable. Finally, the effectiveness of the method and the rationality of the evaluation result are proved by a practical example.