The present disclosure discloses a design method of a soil cover layer of a solid waste landfill considering the effect of plant root, which relates to the field of designing a soil cover for a solid waste landfill and aims to solve the problem of the prior art that does not consider the non-linear spatial variation of water content and the effect of plant root on the gas migration process. By comprehensively considering the type of plant root architecture, the distribution of water content varying with space, the errors of calculating gas migration caused by assuming that the water content of the cover layer is constant and ignoring the effect of plant root is effectively reduced; and the actual environment of the on-site cover layer is more comprehensively considered, thus improving the calculation accuracy.