In order to locate and recognize train numbers, the row projection method can be used to determine the location of skew row of train number. It is also found and proved that the planar correlation between template and scene approximately equals to the correlation of their vertical projection. A fast row scan recognition algorithm and a method of reliability estimation are designed based on this conclusion. Perfect results are obtained by using this technology even for pictures having complex background, verifying illumination, oblique numbers and bad number distributing.