Trust is important in Online Social Networks (OSNs), influencing user interactions, information reliability, and relationship strength. This paper introduces a Fuzzy-based System for Evaluation of User Trust (FSEUT) in OSNs considering four parameters: Attitude (At), Behavior (Bh), Experience (Ep), and Tie strength (Ts). By leveraging Fuzzy Logic (FL), the proposed system evaluates trust more comprehensively, addressing the limitations of existing models that often overlook the role of Ts. Simulation results show a positive correlation between the input parameters and User Trust (UT). The increases of At, Bh, Ep, and Ts lead to corresponding increases in UT. The simulation results show that Ts combined with other factors affect UT in different ways.