The invention relates to a wellhead rock debris removing device in the well drilling process of supercritical carbon dioxide. The wellhead rock debris removing device comprises a cyclone separator and a depositing tank; the cyclone separator is formed in the mode that a cylinder body and a cone body are connected, a CO2 gas inlet is arranged on the upper part of the cylinder body, the bottom of the cone body is provided with a swirl cover and a collection jar, and a center cylinder is arranged at the upper part of the vertex cover; the depositing tank is connected to the upper part of the cylinder body, a gas filter plate is arranged in the horizontal direction in the middle of the depositing tank, a clean CO2 gas outlet is arranged at the upper part of the depositing tank, and a debris discharge outlet is arranged at the lower part of the depositing tank; the cyclone separator and the depositing tank are separated by an oblique spiral separating plate; the bottom of the center cylinder is communicated to the vertex cover, and after the upper part of the center cylinder penetrate the spiral separating plate, the end opening of the center cylinder penetrates through the depositing tank. According to the wellhead rock debris removing device in the well drilling process of supercritical carbon dioxide, cleaner carbon dioxide gas can be separated during construction compared with the cyclone separator, the structure is simple, the operation is convenient, and the reliability is high.