This study studied the ex-situ catalytic pyrolysis of waste polyethylene (WPE) with activated carbon (AC). It was found that the operating parameters and AC/WPE mass ratio had complex interactions on the WPE-AC catalytic pyrolysis oil and gas yields. A hybrid method of artificial neural network (ANN) coupled with genetic algorithm (GA) was used to establish the mathematical expressions of oil and gas yields under different conditions and optimize the conditions to obtain the highest oil yield. The R2 values and the average absolute relative errors between the experimental and the ANN predicted values were 0.9992 and 0.60%, and 0.9830 and 5.01% in the training and the testing tests, respectively. The optimal oil production calculated by ANN-GA was 69.16 wt% under 479 °C, the AC/WPE mass ratio of 1, and 10 mL/min. The experimental oil yield was 69.63 wt% under the optimal parameters, which was close to the predicted value of ANN-GA. The WPE-AC catalytic pyrolysis oils under different conditions were characterized by the Fourier-transform infrared spectroscopy (FTIR) and the gas chromatography/mass spectrometry (GC/MS). The types of oil's functional groups did not change with different operating parameters and AC/WPE mass ratios. The oils were composed of alkenes, naphthenes, alkanes, and aromatic hydrocarbons ranging from C8 to C33. The operating parameters and AC/WPE mass ratio affected the oil fractions to a great extent.