Since the fouling accumulation in the heat exchanger equipment has produced great effect for safe and economical operation,it is particularly important to detect the fouling produced in heat exchanger equipment accurately and rapidly. Ansys finite element simulation software was used to establish the model of hollow and fouling pipelines. Research on the vibration characteristics of ultrasonic guided waves propagate in pipes and the influence of different sources for fouling detection. The optimum excitation frequency and period was obtained for fouling ultrasonic detection in pipes. After compared with the experimental studies,the results indicate that L（ 0,3） mode guided waves motivated by excitation signal with the 1 MHz central frequency and the 10 period signal is adapted to the fouling detection for 304 steel of outside diameter 25 mm and wall thickness 3 mm. The experiment results are in agreement with the numerical results. The guided wave mode and the optimal excitation frequency can be directly applied to the actual detection. The research results lay the foundation for the measurement realization of the fouling thickness in pipes.