The fuel nozzle manufactured by additive manufacturing has significant advantages in shrinking production cycle, lowing cost and boosting qualified rate. However, polishing technology of additive manufacturing fuel nozzle through abrasive flow has become the vital technology that needs to be worked out promptly for additive manufacturing. This research develops a four-factor polishing experiment of abrasive flow for test pieces acquired the characteristics of internal flow path of additive manufacturing fuel nozzle. The result shows that powder adhered to surface, spheroidization effect and step-effect can be eliminated effectively and efficiently by abrasive flow polishing. The optimal process parameters of abrasive flow polishing were obtained by optimization calculation and the surface roughness R_a of the flow channel in the nozzle was reduced from 9.10μm to 2.70μm through the experiment.