The invention discloses a dyeing method of a rayon elastic knitted fabric, and the method comprises the following steps: pre-treating, preshaping, dyeing, soaping, dehydrating, drying, scutching and shaping to obtain the dyed rayon elastic knitted fabric, according to the method, an oil agent and pulp on the fabric in the pretreating process and dir, dust, pigment and the like adsorbed in the weaving and storage and transportation processes are removed; in the dyeing process, phase heating is adopted, and a reactive dye, a leveling agent, sodium carbonate and a chelating dispersant are added,so that the utilization rate of the dye in the production process is improved, the dyeing is uniform, the color fastness is high, meanwhile, the waste water is little, and the energy consumption is low.