A fault diagnosis system was constructed and designed based on EMD correlation dimension, artificial neural network and LabVIEW. The experiment was done with 490BPG model engine when it worked at 1 200 r/min without load. The original vibration signals of valve were decomposed based on EMD method, and then the correlation dimensions of the top four intrinsic mode functions(IMF1～IMF4) were calculated, the correlation dimensions of the IMF1～IMF4 as the input parameters of the artificial neural network were taken and the network model was trained with 80 training samples of four work status, it indicated that the test results of 20 test samples of the experiment conformed to the practical status and the correct rate was 100%. The system could be used online to inspect and diagnose the faults of engine valve clearance. 