Abstract: In order to find out the effect of accidental condition variance of oil pipeline on safe operation, this paper analyzes the typical accidental transient condition based on simulation, and figures out the change patterns of transient pressure and flowrate variation of pipeline by using SPS pipeline simulation software. Results show that flowrate decreases, inlet pressure increases and outlet pressure decreases when some pump station along the line shuts down. While flowrate increases, inlet pressure decreases and outlet increases when pump starts up. When some valve is closed, flowrate going through the valve decreases to zero rapidly and upstream flowrate decreases together with downstream flowrate. And meanwhile, upstream pressure increases while downstream pressure decreases. When pipeline leaks, pressure on the leak point decreases quickly, and upstream flow rate increases, downstream flow rate decreases while upstream and downstream pressure both decrease.These results are instructive to the preparation of emergency plan for pipeline accidents.