Holter recording of electrocardiographic signal (ECG) is usually disturbed by noise added to measured useful signal due to e. g. worse contact skin-electrode, body movements, etc. Our general goal is to find at least some piece of information from ECG (in our case — positions of QRS complexes) in corrupted signal, on which common preprocessing methods fail. The main purpose of the article is description of an automatic method of data preprocessing for QRS detection, which is the first step in our way to final solution. We use Independent Component Analysis based ”filter” that automatically chooses noise-free components. Selection is based on morfology of noise-free ECG components.