A heat dissipation substrate and a seal type PTC (Positive Temperature Coefficient) thermistor heater are disclosed in the present invention, wherein the heat dissipation substrate comprises a cavity body with an accommodating cavity, several heat dissipation fins are respectively fixed on the outside surfaces of the top and bottom of the cavity body, the upper and lower portions of the left inner wall of the cavity body are respectively provided with a first locating rib, the upper and lower portions of the right inner wall of the cavity body are respectively provided with a second locating rib, the left inner surface of the accommodating cavity between two first locating ribs is an arc surface protruding outward, the right inner surface of the accommodating cavity between two first locating ribs is also an arc surface protruding outward, the left and right outer walls of the cavity body are both groove shape structure, the spaces between two first locating ribs and between two second locating ribs are less
