The invention provides a kiln top heat insulation device of a flat-top tunnel type brick kiln. The kiln top heat insulation device comprises a brick kiln top, a calcining kiln body, fireproof brick layers, heat exchanging layers, a heat insulation layer, a heat exchanging pipeline and pressure release holes, the brick kiln top is arranged on the calcining kiln body, two sides of the calcining kilnbody are provided with the fireproof brick layers, each fireproof brick layer is internally provided with one heat exchanging layer, the heat exchanging layers communicate with the heat exchanging pipeline, the heat exchanging pipeline is arranged inside the brick kiln top, the brick kiln top is further provided with the pressure release holes, each pressure release hole is internally provided with a pressure release valve, and the heat insulation layer is arranged between the brick kiln top and the calcining kiln body. According to the kiln top heat insulation device of the flat-top tunnel type brick kiln, the manner that a heat insulation frame walks between an upper installation frame and a lower installation frame is adopted, and the convenience of installation and quickness of assembly are guaranteed; by means of the physical property of heat insulation asbestos inside the heat insulation frame, the temperature inside the calcining kiln body can be retained by the heat insulationlayer; and the heat insulation layer is fixed by the upper installation frame and the lower installation frame, the stability of installation is guaranteed.