The invention discloses a micro-cavity quantum dot laser prepared by capillary force driving and a preparation method thereof; the laser comprises an upper substrate, a bragg reflector on the lower surface of the upper substrate, a heat sealing film and sealing openings, a lower substrate, a bragg reflector on the upper surface of the lower substrate, a quantum dot gain material and a laser pumping source, wherein the upper and lower substrates with the bragg reflectors are thermally sealed together by the heat sealing film to form a micro cavity used for accommodating the quantum dot gain material; the two end sealing openings of the heat sealing film are sealed by ultraviolet curing glue; and the quantum dot gain material adopts a high-concentration quantum dot solution with the concentration of 50-120 mg/ml. The wavelength of the quantum dot laser device can be modulated along with the size change of the quantum dots; and the preparation process is simple, and the repeatability andthe stability are relatively high. The laser has quite high light gain under the short-wave laser pumping, the coherence is very high, the light emitting wavelength can be adjusted in a full-visible spectrum range along with the light emitting peak position of the quantum dots, the preparation cost is low, and large-scale industrial production can be realized easily.