The invention discloses a potential type gas sensor based on a Li3PO4-Li4SiO4 mixed solid electrolyte and a preparation method thereof. The preparation method comprises the following steps: preparing a membrane type Pt resistance temperature measurement electrode and a Pt heating electrode by a silk-screen printing method on an Al2O3 ceramic substrate; depositing a Li3PO4-Li4SiO4 mixed solid electrode film on the polished surface of the Al2O3 ceramic substrate by an electron beam evaporation coating technology; and depositing an electrode Au film by a magnetron sputtering method, and printing a chemical material on the surface of the electrode Au film to form a potential type gas sensor of solid electrolyte finally. In the sensor, a Li3PO4-Li4SiO4 mixed solid electrolyte layer is adopted, and the ionic conductivity at relatively low temperature can reach the level of Li3PO4 solid electrolyte at relatively high temperature; and moreover, with a closed-loop temperature control system, multiple functions of reducing the sensor working temperature, lowering the power consumption, increasing the response rate, enhancing the output stability, realizing time control and output and the like are improved.