Abstract: In view of long-standing in solving the problem of complicated systems by Electromagnetic Compatibility (EMC) testing when the products have been produced, as a result, the products may be ‘over designed爷or ‘weakly de signed爷. The paper takes a link layer as an instance, analyzing the link layer performance influenced by Electromagnetic En vironment Interference, therefore establish a statistic model about the link layer. According to the character of Electromagnet ic Environment in randomicity, some methods about the analysis of Electromagnetic Environment Effects (E3) are discussed. With these criteria, it can be ensured to evaluation of E3 and prediction for complicated systems such as space link layer .