Coal spoil heaps can occupy large areas of land and cause serious environmental problems. This paper describes a study on the influence of arbuscular mycorrhiza application in the re-vegetation of coal spoil heaps under field conditions at Dawukou coal processing plant, Ningxia Province, north China. Inoculation with arbuscular mycorrhiza increased plant survival rate by 15%, promoted plant growth and enhanced plant cover by 9% and biodiversity within 13 months of inoculum application. The percentage of total root length of mycorrhizal plants colonized was up to 90% higher and the hyphal length on mycorrhizal plants was 1.4 times greater compared with non mycorrhizal controls. External hyphae can increase the volume of soil explored by the roots and help the plants to tolerate poor soil conditions to enhance the stability of plant cover in the re-vegetation of coal wastes.