For detecting two motion states of a moving object in a single frame image,a nov el method is proposed for in-plane displacement and velocity measurement based on a single frame image by using an interlaced scanning camera.One frame image is recorded by a n interlaced scanning camera for a in-plane moving object,and is composed of odd and even field images during a recording interval of one field period,each of which is operat ed by Fourier transform de-interlacing a lgorithm,and the quality of de-interlaced image is identical with that of the corresponding frame image of the single fiel d.According to the different reflectivities of the object and background,the object′s outline is extracted from each de-inte rlaced image to obtain binary template,which is operated to compute the centroid to get sub-pixel location precision.The two matching points are calibrated to obtain the space coordinates,and displacement and average vel ocity are calculated in one field period.In the experiment for an object with in-plane constant velocity,t he maximum absolute error of measured velocity is 0.35mm/s,and the relative error is 0.78%.The results demo nstrate that the method can effectively measure in-plane displacement and veloc ity.