Abstract: Preparation technology of pectinase treatment to pectin and insoluble substances,such as cell membrane fragments,from blood orange pulp- wash liquid was optimized.The light transmittance,as index,was investigated with respect to pectinase dosage,p H,reaction time and temperature by single factor experiments and L_9( 3~4) orthogonal experiments.After the pectinase treatment,the concentration rate of pulp- wash liquid and physical- chemical indexes of molasses products were analyzed and compared.The results showed that optimum conditions of pectinase treatment were amount of pectinase 0.076 U / m L,p H4.0,reaction time 1.5 h and temperature 35 ℃. At the end of concentration,the concentration rate of enzyme treated liquid was significantly accelerated.The reducing sugar content and purity of molasses made by enzyme treated liquid were respectively increased by 7.91% and 2.99%,while the content of pectin and protein were respectively decreased by 81.25% and 61.78%.