The invention discloses a variable width combined chain type heading machine which comprises an excavating main body. The excavating main body comprises a front cabin and a back cabin hinged to each other, wherein each of the front cabin and the back cabin is formed by splicing a plurality of structural bodies. By adjusting the quantity of the structural bodies, the excavating width of the whole chain type heading machine is adjusted. According to the chain type heading machine, the angle of inclination of a soil cutting chain panel is adjusted by adjusting the degree of elasticity of an oil cylinder, the overbreak quantity is controlled precisely, and the variable width combined chain type heading machine is guided to meet an excavating curve; and the variable width combined chain type heading machine can be integrally disassembled and assembled quickly, so that the mounting efficiency and the maintenance efficiency are improved.