The measurement of modulation transfer function (MTF) of the sampled imaging opto-electronic system is rather complex and irrepeatable for their shift-variant characteristics. Based on the theory of statistical optics and stochastic process, the correlation relationship of spatially discrete random signal pattern and its correspoding image through a linear optical imaging system are analyzed. A method using random bar pattern for modulation transfer function measurement is proposed, and the emulational experimental result is demonstrated. The random bar pattern test method reduces the effect of sample-scene phasing of sampled imaging device in statistical sense. This method is also adapted to the MTF measurement of commonly shift-invariant optical system and is expected to greatly improve the flexibilities and automation degree of MTF testing.