The invention relates to a preparation method for an attapulgite nanometer particle polyimide composite fiber. The preparation method comprises the following steps of: doping attapulgite nanometer particles with high purity into an aprotic polar solvent containing polyamic acid by adopting an in-situ polymerization method, spinning and forming through wet (dry-jet wet-spinning) spinning, and then obtaining the polyimide fiber containing the attapulgite nanometer particles by cyclization and hot-stretching. By adding the attapulgite nanometer particles, the mechanical property of the polyimide fiber can be improved, and the heat resistance stability of the polyimide fiber can be obviously increased; the preparation process is simple and practical and is free of pollution to environments; and the heat resistance and the mechanical property of the obtained nanometer polyimide composite fiber are greatly increased so that the nanometer polyimide composite fiber has good application prospect.