Twin-reversed arterial perfusion (TRAP) sequence is a rare complication in monochorionic pregnancies, in which a normal pump twin provides blood to an abnormal acardiac twin.One of the fetuses has an absent or nonfunctioning heart(acardiac twin) and depends on the normal co-twin to receive blood perfusion.The acardiac twin is a true parasite receiving blood from the pump twin through an artery-to-artery anastomosis in the placenta.The application of Color Doppler Ultrasonography and power Doppler techniques to every monochhorionic pregnancy with clinical manifestation of an anomalous twin allows easy establishment of the diagnosis.Magnetic resonance imaging can provide a complementary modality in evaluation of the pump twin for congenital anomalies, detecting signs of acardiac decompensation and complication of cardiac overload and chronic hypoxia, especially intracranial defect.The mortality of the acardiac twin is 100%, while the pump twin also runs a high risk of perinatal mortality due to heart failure and prematurity.Conservative management with close monitoring and active management, interrupting the vascular connection between the pump twin and the acardiac twin, are the available options forTRAP.Early evaluations such as the color Doppler Ultrasonography and prompt intervention including fetoscopic laser coagulation, intrafetal radiofrequency cathete ablation and high-intensity of focused ultrasound (HIFU) , may improve the survive of the pump twin considerably.We report a case of TRAP sequence in monochorionic-monoamniotic pregnancy with acardiac-diamniotic twin and favorable outcome for the pump twin.