Abstract: 2,2-dimethylol-1-butanal(DMB) was synthesized by n-butyraldehyde（NBAL）with paraformaldehyde（PFA）in the existence of triethylamine（TEA）. NBAL reacted completely(＞99％) and the yield of DMB reached 88%.The structure of DMB was characterized by IR、GC、GC-MS、¹HNMR.It was found that the concentration of TEA and H₂O greatly affected the rate of temperature rise of the reaction system and the yield of DMB. The optimized reaction conditions were as follows:under the nitrogen atmosphere,n_NBAL∶n_PFA∶n_TEA=1∶3∶(0.05—0.1)and 10%—15% water by weight, temperature 50—80℃,reaction time 2h.