The composite electroslag melting and casting technology was adopted to produce WC particulate reinforced steel matrix composites with two kinds of particle size and 45wt% WC content.Thermodynamic analysis was carried out on the WC in composite electroslag melting and casting process, assisting by SEM, EBSD and EDS, and the measurement and calculation method of Sierpinski fractal dimension was used for the fractal study on composite materials before and after heat treatment.The results show that in WC particulates reinforced steel matrix composites, WC form shows a dominant position, and displays in a triangle or rectangle.WC grains take (0001) surface as a reference plane, then grow up into a stack structure in the way of hierarchical form along the direction < 0001 >, finally form a three-dimensional shape with the surface (0001)in a triangle.The fractal dimensions of WC present different changes with the transformation of the heat treatment process.When quenching and tempering at high temperature, fractal dimension value of two types of WC appear, and WC phases show two groups of different fractal structure with different particle size and quantity.The larger fractal dimension difference ΔD corresponds to Fe3W3C compound carbides, with the smaller ΔD to WC particles which keeps the properties and morphology under the state of forging and annealing.The higher the quenching or tempering temperature, the larger the fractal dimension difference ΔD, and the greater change of the morphology of WC.