The assessment to environmental risk is the effective method to manage risks in contaminated sites. To design the assessment standard of environmental risks on contaminated sites, it is necessary to consider the subjective, objective, purposeful, distinguishing and dynamic nature of risk recipients. The impact factors also include the characteristics of contaminated sites risks, the characteristics of risk recipients, the level of risk management and economical development. It will be helpful to manage, control and decrease the risks to have an assessment standard based on the numbered method of environmental risks on contaminated site.