Ni3Al based single crystal alloy IC6SX was prepared by election spiral crystal method. The effect of the conical transition section of the single crystal on the microstructure of the single crystal was studied in this work. The results showed that, in the crystal growth process, the effect of the conical transition section on the orientation of single crystal was significant. The yield ratio of the single crystal alloy specimen with <001> orientation could be improved significantly by adding cone transition section. With the angle of the cone transition section increasing from 20 º to 43 º, the dendrite arm spacing increased gradually, and dendrite morphology was coarsened and the third dendrite arm appeared.