Micro injection molding is competitive for fabrication of polymer-based micro-fluidic chips because of its high productivity. Unlike hot embossing, injection molding will not provide even molding condition for everywhere of the molded part. So the microchannels of an injection molded micro-fluidic chip need to be checked everyplace, while a hot embossed micro-fluidic chip can be checked only by one slice of the microchannels if only the micro protrusions of the mold stamp remain the same cross-sectional figure. Because an injection molded micro-fluidic chip has characteristics that its replication of the micro stamp protrusion is perfect in height but not satisfactory in width, especially for the width of the micro protrusion’s root which matches the molded microchannel’s opening, in this study micro flat photos of injection molded micro-fluidic chips were processed by our own image processing system developed from the image box of Matlab software. Measuring data about microchannels width from the micro flat photos were compared with measuring data obtained from a cross-sectional photo of one slice of the microchannels. Difference between data of these two measuring ways was less than 2% for opening width of the molded microchannel. So by image processing of the micro flat photos, rapid overall non-destructive testing of micro replication can be carried out for injection molded micro-fluidic chips.