Aiming at the problems that the fetal electrocareliogram（ECG） signal in the mixed ECG signal of the mother's abdomen is weak，contains a lot of noise，and is difficult to be extracted clearly，this paper proposes a method based on singular value decomposition （SVD），smooth window （SW） technology and least square support vector machine （LSSVM） new method of fetal ECG extraction. Firstly，SVD is used to reconstruct the decomposition matrix from the single-channel maternal abdominal ECG signal in order to estimate the maternal ECG reference signal，and the SW method is used to smooth the estimated maternal ECG reference signal；then，LSSVM is used to establish a non-linear estimation model，the maternal ECG component in the abdominal signal is estimated through the model and the smoothed maternal ECG reference signal，and the cuckoo search algorithm（CS） is used to optimize the hyperparameters of LSSVM. Finally，the mixed abdominal signal is subtracted from the maternal ECG component estimated by the CS-LSSVM model so as to obtain the preliminary fetal ECG signal. To further eliminate the interference，the SW-SVD operation is performed on the initially obtained fetal ECG signal，thereby obtaining a clearer fetal ECG signal. Experiments with Daisy data set show that the method proposed in this paper is superior to the other three classic methods in visual comparative analysis and four statistical evaluation indicators，and can extract clearer fetal ECG signals from the mixed abdominal signals.