Recently the particle analysis of hard materials with complex phases, such as cemented carbides and Mo₂FeB₂ base hard alloys, has been performed by using an image analyzer. But a conventional algorithm of the image analysis has some difficulties to get accurate measurements of the microstuructural parameters, such as a mean particle size, contiguity and aspect ratio of hard partcles. To solve this problem, a new algorithm for grain boundary detection has been developed by using a back-scattered electron image, which shows electron channeling contrast (ECC) depending on the crystal direction difference in the aggregated hard particles. By applying this method to the Mo₂FeB₂ base hard alloys, it is quantitatively elucidated that the transverse rupture strength (TRS) drop at lower sintering temperature is due mainly to the coalescence of the hard particles.