The invention relates to a method for preparing a Tb-Co alloy layer by utilizing ionic liquid electrodeposition technology, in particular to a method for preparing the Tb-Co alloy layer, aiming at solving the problems of complicated manufacturing technique and equipment, high cost and uneven surface of a settled layer when the Tb-Co alloy layer is prepared by the prior art. The preparation method comprises: 1. 1- methyl-3- butyllnildaanlium tetrafluoroborate, anhydrous cobalt fluoroborate and anhydrous terbium fluoroborate are mixed together for preparing ionic liquid electrolyte; 2. electrodeposition; 3. after being washed by ethanol and distilled water and dried, the sample is dried to obtain the Tb-Co alloy layer. The method utilizes the ionic liquid electrodeposition technology to synthesize the smooth, flat and uniform Tb-Co alloy layer. The invention has simple technique and equipment as well as low cost.