Abstract: Diagnosis of incipient faults for electronic systems especially for analog circuits,is important yet difficult.The paper proposes a new method using HMM for the diagnosis of the incipient faults in analog circuits.First,the voltage feature vectors are extracted from analog circuits;Then,the improved LDA is used to reduce dimensionality of the voltage feature vectors and remove their redundancy,where the performance of LDA is improved through overcoming shortcomings existing in original LDA;Finally,the processed feature vectors are used to form the observation sequences,which are sent to HMM to accomplish the diagnosis of the incipient faults.The experimental results on performance of the proposed method indicated that the method has better recognition capability than the other methods.