A fast and robust skew detection for scanned document images based on the improved piecewise covering by parallelograms is proposed in this papper. Comparison with the original PCP algorithm, the skew detection of the proposed algorithm is more applicable on vertical textlines documents, and is not sensitive to the noise. The experiment results show that the computation time is short, while the detection accuracy is higher. The enhanced skew detection approach is efficient for horizontal and vertical textlines documents, and the complex documents with forms, tables and pictures.