Active power systems have been used in power system intensively. Selection of a suitable filter is very important to solve power quality problems perfectly. Since filter selection depend on a lot of parameters of power system, decision support systems can be employed in filter selection. In this paper, "An Intelligent Decision Support System, IDSS" is proposed. The system determines efficiency of three phase shunt active power filter for the power quality problems. The system developed converts the parameters obtained into the useful data at rule-based inference mechanism then the useful data are evaluated in Naive Bayes classifier. Thus a low cost decision support system has been developed to guide the users in the rate of suitability of three phase shunt active power for solution the power quality problems.