The inherent reliability of heat exchanger in the design and manufacturing process, such as welding manner, yield strength, etc., has been the subject of many studies in the past. However, the operation reliability of heat exchanger, such as temperature, pressure and fouling resistance has received less attention. Herein, a novel heat exchanger reliability model involving the fouling resistance was established based on the Fault Tree Analysis (FTA). Moreover, a time-dependent progressively fouling growth model was also developed. In addition, Fouling Resistance Probability (FRP) was defined and calculated as a reliability indicator, which represents the failure probability of heat exchanger caused by fouling resistance. Subsequently, the well-established progressively fouling growth model was incorporated into the FTA model as a basic event. Ultimately, the heat exchanger reliability based on the FTA model was presented. Finally, maximum value of the heat exchanger failure rate originated from fouling growth was determined to be around 0.340 through three case studies in the literature, and minimum value of the heat exchanger unit reliability was estimated to be about 0.501. For this reason, the fouling resistance has a pronounced influence on the reliability of heat exchanger.