Abstract: For developing a high-efficient, energy-saving and environmental-friendly low temperature dyeing technology of disperse dyes, the role of novel promoter BEA in low temperature dyeing of polyester fiber with disperse dyes was investigated. The effects of BEA on the solubility of disperse dyes in water and on the glass transition temperature of polyester fiber were studied by solubility experiment and differential scanning calorimetry (DSC), and a series of corresponding dyeing experiments were carried out. It was found that BEA promoted solubilization of disperse dyes and had plasticizing effect for polyester fiber, thus promoter BEA exhibited excellent accelerating dyeing action. However, There existed an optimal concentration of the promoter, i.e., 0.8 g/L when the disperse dyes concentration was 6% (o.w.f) and the dyeing temperature 108℃. Around this concentration, the addition of BEA into dye bath can improve the dyeing rate, dye uptake and K/S value obviously, and its good dyeing accelerating effect makes it possible that the dyeing result of low temperature dyeing is close to, or even better than, those of high temperature and pressure dyeing.