The invention relates to nitrogen fertilizers, in particular to a multi-functional slow-release urea fertilizer and a preparation method. The fertilizer comprises urea, a biochemical inhibitor, synergist, water-soluble salt ions of secondary and trace elements necessary for plants and / or beneficial elements for plant growth. By weight percentage, the weight percentage of the urea to the biochemical inhibitor to the synergist is equal to 1: 0.001-0.1: 0.0005-0.05, the salt ions of the secondary and trace elements necessary for the plants comprises one kind or a plurality of kinds of calcium, magnesium, sulfur, ferrum, copper, zinc, manganese, boron, molybdenum and chlorine, the weight percentage of the urea to all the secondary and trace elements necessary for the plants is equal to 1: 0-0.1: 0-0.1: 0-0.06: 0.001-0.03: 0.001-0.01: 0.001-0.01: 0.001-0.008: 0.001-0.01: 0.001-0.005: 0-0.006, the beneficial elements for the plant growth comprise silicon and selenium, and the weight percentage of the urea to all beneficial elements for the plant growth is equal to 1: 0-0.1: 0.001-0.08. The multi-functional slow-release urea fertilizer can promote growth of root systems, invigorate plants, enhance disease resistance, drought resistance and lodging resistance, and stimulate prematurity.