A conical solid-liquid separator includes a separator body, a clean water collection tank and a wastewater collection tank provided at an upper surface of the separator body, a conical sieves provided at the top of the clean water collection tank, an arc cone sheathed on the top of the conical sieves and having an upper end connected an inlet pipe. With the installation of the conical sieves, wastewater flows from the inlet pipe into the arc cone and then passes through the arc cone to disperse the water flow and enters into the conical sieves for filtering. The conical solid-liquid separator and its operating process are simplified to reduce water consumption and improve the processing efficiency. In addition, the conical solid-liquid separator comes with a simple and compact structure and reduces the power consumption significantly.