According to the requirement of large civil aircraft manufacture, experimental study of the deep hole machining of 155PH stainless steel was conducted. The influence degree and law of spindle speed, feed rate and hole depth to hole diameter deviation at exit was respectively illuminated using range analysis method. Besides, multiple regression analysis was applied to construct the index prediction model for hole diameter at exit. The experimental and analysis result shows that the main influence factor to the hole diameter deviation is hole depth. Meantime, by comparing between predictive value and experimental value, the rationality and effectiveness of the prediction model of hole diameter is verified. 