Diethylaluminum azide (DEAA) is an important compound in organoaluminum andes. But the synthesis and property of DEAA were reported a little. The DEAA is a liquid compound in literature that was synthesed by the reaction of diethyl aluminum chloride (DEAC) and sodium azide. The solid product as a colorless crystal was first obtained by the reaction of DEAC and sodium azide in our work. The solid product was characterized as DEAA by IR spectrum and H NMR spectrum. The yield of crystal DEAA was increased as NaN3/DEAC (mol/mol) increased. When NaN3/DEAC = 1. 3 the yield of DEAA is increased from 74% in literature to 83%. The melting point of DEAA is 28 - 29℃ that was determined with two methods in the work. The DEAA containing trace DEAC (about 0. 2% of DEAC) is liquid which has been full proved by varied tests in this paper. The melting point of DEAA is - 130℃ in literature because the DEAA is not pure that may contain DEAC. The - 130℃ may be eutectic point of eutectic mixture forming of DEAA and DEAC. 27,Al NMR of DEAA is determined. At δ = 6. 4 there is a peak that 1/2 of the peak is 834Hz. The structure of crystal DEAA is inferred from 27Al NMR.