Location of marker points is an essential previous work in FPC（Flexible print board） automatic inspection process.The center of the FPC solder is selected as marker point.Aiming to the solder’s deformation when locating the marker points，the concept of directional entropy is proposed to describe the distribution of inspecting objective contour’s direction，which is applied in extracting solder’s contour and directional feature.Then the contour similarity function is established.The valuable contour is reversed and adopted to match solder，and marker’s location is also realized finally.Experiments show that the marker’s locating accuracy is improved，inspecting objective’s positioning error is reduced through image registration based on affine transformation，which is within 60 μm.It is significant for practical applications especially the consequent inspecting work such as defect analysis and defect detection.