Maintenance activity to equipment is very important for production process and safety. It has a vital role to play in reducing the risk associated with some workplace hazards and providing safer and healthier working conditions. However the maintenance activity is an disadvantage for improving production rate, and it`s not good for economic budget. So sometimes the company decide to defer the maintenance activity. In this paper we will talk about the methodology for testing the risk of deferred maintenance. With respect to risk assessment analysis, fuzzy logic is a more efficient methodology. With the help of professional experts, we can define the membership function and precise rule for every considerable variable and every possible condition.