In aerial photogrammetry, image motion blur due to aircraft forward flight and rotation is one of the error resources in image coordinate measurement, which could lead to misalignment in collinearity equation and accuracy decline in direct georeferencing. For the purpose of analysis the influence of image motion blur on direct georeferencing, the motion blur of frame imagery was modeled based on collinearity equation with consideration of both ration and translation movement. The linearity approximation equation was also derived. Analysis shows that the centroid of smear track could be used as image point in intersection only with mid-exposure time as the nominal photo exposure time to eliminate the blur problem in image measurement. Simulation result shows that maximum RMS in object space could be reduce to 0.12 mm by using the method above.