The present disclosure provides a preparation method of a contact material with high thermal stability and low contact resistance based on an MgAgSb-based thermoelectric material and relates to the field of the contact materials preparation. The present disclosure aims to solve the problem of failure to achieve long-term stability for the MgAgSb/Mg3Bi2 device due to the fact that a contact material used by MgAgSb is Ag and MgAgSb may easily yield Ag3Sb in an Ag-rich environment at present. The method includes: at step 1, preparing MgCuSb nano-powder; at step 2, preparing MgCu0.1Ag0.87Sb0.99 nano-powder; at step 3, preparing MgCu0.1Ag0.87Sb0.99—Mg3.2Bi1.5Sb0.5 thermoelectric generation device. The present disclosure is applied to preparation of a contact material with high thermal stability and low contact resistance based on an MgAgSb-based thermoelectric material.