X-ray phase contrast imaging is of high sensitivity,with which the internal structure of light elements can be observed. It shows the promising application prospects in many fields such as medicine,biology and material science,etc. Grating imaging successfully used the incoherent source,which brought us into a new epoch of incoherent source phase contrast imaging. A new phase-contrast CT method is developed by introducing the helical scanning into the field of phase-contrast imaging. By analyzing the feature of incoherent source in helical trajectory,a fan-beam helical phase contrast extracting method is presented and by referring to Hilbert′s filtered backprojection reconstruction algorithm,the fan beam helical phase-contrast imaging CT reconstruction algorithm based on grating imaging is proposed. Phase information is reconstructed directly by the refraction projection according to the proposed algorithm computer simulations and performance analysis demonstrate the efficiency of the proposed method.