Abstract: Experimental study on deep hole drilling of 30CrMnSiA alloy steel was conducted by orthogonal design method. The influences of drilling parameters such as spindle speed, feed rate, and hole depth on the aperture deviation in 30CrMnSiA deep hole drilling were studied. Range analysis is applied to evaluate the influence of various drilling parameters on hole diameter deviation and it can be seen that the hole depth is the main influence factor of hole diameter deviation. Meanwhile, the prediction model of the holediameter deviation is carried out by using partial least squares method. Comparison between predictive value and experimental value reflects that the mean absolute error is small, verifying the reasonableness and validity of prediction model.