The invention provides a method for constructing an ecological side slope. The constructing method comprises the steps that bagged soil is laid on a side slope foundation, the bagged soil comprises flexible bags and soil contained in the flexible bags, and plants are planted on the bagged soil; the soil contained in the flexible bags is mixed with microbial agents; the microbial agents include bacillus licheniformis, and the preservation serial number of the bacillus licheniformis is CCTCC NO: M2013497. According to the technical scheme, the method can obviously promote the roots of the green plants to grow in the side slope and reach the higher development degree, and therefore the stability of the side slope is further increased.