The invention discloses a rapid crystallization type nanometer composite polyester hot melt adhesive and a preparing process thereof. The preparing process mainly includes the following steps: adding a certain amount of dimethyl terephthalate and other dibasic esters, 1,4-butanediol and other dihydric alcohols, organic montmorillonite, nanometer silica and cobalt acetate serving as the catalyst into a reactor, performing transesterification reaction under protection of nitrogen until the quantity of distillate of by-product monohydric alcohol occupies more than 95% of the theoretical quantity; and performing heat preservation for some time, adding stabilizing agents and antimonous oxide which serves as the polycondensation catalyst, continuing to raise the reaction temperature, and conducting decompression and polycondensation to obtain a target product. The obtained product has the advantages of being short in opening time, good in heat resistance, strong in dry cleaning resistance and rinsing resistance, low in cost and the like, and is widely used in synthetic fiber bonding.