The invention discloses a detachable extending-retracting coal mining system comprising cutting units and a traction unit. The cutting units comprise cutting positioning assemblies and cutting movingassemblies. A hydraulic braking device is arranged in the traction unit and comprises a traction power assembly; the traction power assembly comprises a traction driving piece, a traction connecting piece and a traction conveying piece; and the traction driving piece and the traction conveying piece are connected through the traction connecting piece, and the traction connecting piece penetrates through the center of the traction conveying piece. Through arranged automatic extending-retracting structures, automatic extending-retracting protection of the cutting units can be achieved, and the service life of appliances is prolonged; rocking arm connecting parts, rocking arm fastening parts and rocking arm limiting parts are arranged in the positions, connected with water pipes, of a coolingdevice so that connection loosening of the water pipes and heat exchange pieces due to vibration in operation of the coal mining machine can be avoided, the separating situation due to unstable connecting and fixing of the structures is prevented, and accordingly normal using of the coal mining machine is facilitated.