This paper deals with the processing one of the most important biological signals. Interpretation of data taken from cardiac monitoring reveals useful information about individual health. The main purpose of the paper is to use numerical methods to interpret the electrocardiogram signals more accurately and detection QRS complex. All the data used in this article is from the MITBIH database . The basic functions of the wavelet transforms have been tested with 3th and 4th decomposition levels on 1000 data (10 seconds of normal and arrhythmia heart rate).