The analysis of Electrocardiogram (ECG) signal is Very cumbersome due to its non-stationary nature. ECG signal is the combination of P-wave, QRS-wave and T-wave. 11-peaks detection is very important for classifying heart diseases in QRS-wave. R-peaks detection is not easy task due to the involvement of various types of noises and large length of data sets. In this work, discrete wavelet transform (DWT) is considered for preprocessing step. Hilbert transform has been used for spectral estimation for the step of extracting features. Finally, principal component analysis (PCA) is adopted for reducing feature vectors. R-peaks have been detected from reduced features on the basis of calculating the variance of principal components (PCs). The detection sensitivity (SE), positive predictivity (PP), F-measure (F-m) and mean squared error(MSE) are estimated for evaluating the performance of the proposed technique. It gave 99.88% SE, 99.88% PP, 99.88 % F-m, and 0.0766 MSE.