Abstract: The paper presents an algorithm based on PDF417 two dimensional bar codes' structure. It first proposes a filter to eliminate noise, then deals with vertical scratches and those points that do not comply with the bar codes' boundary characteristics by a point-search strategy. Later, during process of restoring the bar coded pictures, the contaminations will not be restored because-their seeds for restoration have been cleaned beforehand. This algorithm features a reliable picture restoration that is free from the negative consequences imposed on the effective bar code edges by filtering. The restored pictures can be decoded by the improved edge-detecting projection method. Experiments have proved that this algorithm improves efficiency and accuracy of the decoding process while demanding a lower error correcting level.