Objective To find out the clinical outcomes of twin-twin transfusion syndrome (TTTS) after aminioreduction. Methods Twenty-nine pregnancies with TTTS delivered in Beijing Gynecological and Obstetric Hospital from Nov. 1, 2002 to Sept. 30, 2007 were recruited. The effect of gestational age at the onset, the degree of TTTS and amnioreduction therapy on the fetal outcomes were compared. Results All of the 8 cases with the onset of TTTS before 26 weeks without treat- ment were lost, but 4 out of the 6 with the onset after 26 weeks survived (P=0. 015). Among the 9 cases received amnioreduction, 4 out of the 5 with onset before 26 weeks survived, and significant difference was found compared to those untreated ones (P= 0. 007), but no difference was shown when compared with those developed after 26 weeks(4/4)(P= 1. 000). The average delivery weeks in the untreated ones was earlier than those received treatment E(28.7±4.7)weeks vs (33.2±4.9) weeks, P=0. 001]. Amnioreduction improved the umbilical cord blood flow. For severe TTTS(stage Ⅲ～Ⅳ) with the onset before 26 weeks, the survival rate after amnioreduction was significantly high- er than those untreated ones[4/5 vs 0/5, P=0. 048)]. Conclusions Aminioreduetion is effective in improving the cord blood flow, prolonging the pregnancies, and achieving a higher fetal survival rate.