The Trips selection will become even more important nowadays especially as online trips in large trips databases can be used to give online travelers a better choice of trips than can be found off-line.The process of selecting a trip is considered as one of the most difficult stages a traveler goes through, especially with tens of trips of similar goals, different prices and detailed characteristics in the market.This paper is interested in proposing a Decision Support System to select the optimal Trip that meets each traveler's preferences; using Case- Based Reasoning techniques ' CBR', and calculating similarity between the traveler's preferences and the trip characteristics.