The utility model discloses a single-frequency microchip laser, the frequency-select element of the laser comprises of a double-refraction crystal plate and combination prisms. The combination prisms consist of front, middle and the rear parts made by the same double-refraction crystal material and the light axis of three parts are on the same plane. The light axis of the front and the rear parts are paralleled with crystal section, the axis of the middle part has an angle with the axes of the front and the rear parts separately. Through the combination prisms, the o-light is transmitted and the e-light is reflected. Using the above structure, fundamental frequency light incident to combination prisms are decomposed of o-light and e-light components, wherein the e-light component is lost due to the deflection out of the cavity, the o-light polarization in combination prisms is minimal for different wavelengths generate different e-light components, so the single-frequency output can be achieved for the minimum wavelength e-light component achieves oscillation.