The invention discloses a steam cylinder boring machine with double boring cutter bits and a method of the steam cylinder boring machine. The steam cylinder boring machine comprises a base, workbenches, uprights, balancing weights, chains, chain wheels, spindle boxes, lead screws, nuts, lifting motors, spindle motors, boring cutter seats, belt pulleys, rough boring cutters and fine boring cutters. Each spindle motor drives the corresponding boring cutters to move synchronously on the corresponding spindle box through belt transmission, the rough boring cutters and the fine boring cutters move at the same time, and after rough boring is finished, rough boring and fine boring can be rapidly switched through the movable workbenches. The method is simple, the requirements for the technique of workers are low, and the production efficiency of bored holes can be effectively improved.