The invention relates to a greening method suitable for a greening forest of a northern city. According to the technical scheme, (1) a method for greening under trees comprises soil improvement, graveling, building of enclosing walls, earth filling, watering, settlement, earth supplementation and planting and management of fragrant plantain lily herbs; (2) a method for greening among trees comprises construction of water storage layers, modeling around the trees, soil improvement, planting and management of potentilla centigrana for slopes around the trees and planting and management of mixed ground cover plants of festuca rubra and sedum sarmentosum bunge among tree slopes. According to the method, the exposed earth surface of the greening forest is covered with green plants by virtue of special technical measures according to a multilayer greening mode under the condition that an urban planned greening area is kept unchanged, so that the greening area is enlarged, raising dust on the exposed earth surface is prevented, and the air quality is improved.