Axial flow pump motor is a type of permanent magnet micromotor, which has small volume, high flow rate and good stability. It is more widely used in artificial heart. The winding of general brushless DC motor often adopts star connection method, while the winding of axial flow pump motor is usually designed as coreless winding, so its winding generally adopts triangular connection method. When the sensorless control is applied to the axial flow pump motor, the traditional back EMF zero crossing detection method used for star connection method is no longer applicable. Therefore, a new back EMF zero crossing detection method is proposed to realize the sensorless control of the axial flow pump motor. The experimental results show that this method is suitable for the axial flow pump motor with triangular connection.