The invention discloses a preparation process of a modified polylactic acid-rosin polyether polyatomic alcohol composite material. According to the process, the modified polylactic acid-rosin polyether polyatomic alcohol composite material is prepared from rosin, maleic anhydride, polyisocyanates, polyurethane, sodium citrate, toluene diisocynate, glycerol, polylactic acid and the like as raw materials through the steps of optimizing the parameters of repeated vacuum pumping reaction and nitrogen gas filling pressurized reaction and creatively adding high-temperature water vapor for high-temperature degeneration. The prepared modified polylactic acid-rosin polyether polyatomic alcohol composite material has the advantages of high compressive strength, good heat conduction performance, excellent thermal stability and better application prospects.