Abstract: When conditions are ready, the commissioning trial of product oil pipeline will follow the order in commissioning the station equipment and subsystems, purging of trunk line, water filling of pipeline, overall commissioning of whole line with water, commissioning with oil, product offtake operation (commissioning of branch lines) and so on. The paper elaborates the aim, content and implementation procedures of each step, explains the applicable conditions of direct commissioning and oil-after-water commissioning, introduces different ways of establishing back pressure before the oil head when direct commissioning is used on product pipelines of big elevation, and points out that as stable oil water mixture is apt to form at the low spots of hill product pipeline, it is better to take the oil-after-water way to commission such pipeline.