The invention discloses a blue-light perovskite light-emitting diode and a preparation method thereof. The structure of the blue-light perovskite light-emitting diode sequentially comprises a substrate, an anode, a hole transport layer, a light-emitting layer, a passivation layer, an electron transport layer, an electron injection layer and a cathode from bottom to top, wherein the light-emitting layer is a perovskite thin film prepared from a perovskite precursor solution; when the blue-light perovskite light-emitting diode is prepared, a perovskite thin film is prepared through a perovskite precursor solution added with a thiocyanate additive, so that the thin film morphology of a light-emitting layer is adjusted through the thiocyanate additive; and after the perovskite thin film is prepared, the perovskite thin film is subjected to passivation treatment, so that the performance of the perovskite thin film is improved. The perovskite thin film is prepared based on the additive engineering of the perovskite precursor solution added with the thiocyanate additive, and the surface passivation treatment is utilized, so that the surface defects of the thin film are further reduced, and the light-emitting performance of the blue-light perovskite light-emitting diode is improved.