The invention discloses a PE/PET composite ultra-short non-crimp fiber post-treatment production method and device. The production method comprises the steps of pre-spinning precursor bundling, dipping bath, primary tow stretching, secondary tow stretching, tow crimping, tow laying, tow loosening and shaping, tow cutting, packaging and the like. The corresponding post-treatment device comprises a bundling frame, a dipping bath tank, a water bath tank, a steam drafting box, an oiling machine, a yarn stacking machine, a crimping machine, a drying setting machine, a cutting machine and a packaging machine which are sequentially arranged on a workbench from left to right. Through specific post-treatment method including dipping bath, drafting, crimping, shaping and cutting, the melting point of the skin layer of the prepared PE/PET composite ultra-short non-crimp fiber can be reduced, the bonding strength of non-woven fabric is improved, the doping proportion of the fiber is reduced, and the downstream production cost is reduced.