Abstract: In order to make risk assessment on oil/gas pipeline more accurately, on the basis of principle component analysis and clustering analysis, the paper establishes risk assessment model of oil/gas pipeline based on principle component- clustering analysis, and uses this model on the risk assessment of a inland gas pipeline. According to the established risk assessment process, by using numerical standardization and statistical analysis, the correlation and weight subjectivity between pipeline risk indexes are lowered, 3 principle component factors of pipeline risk indexes are proposed, then according to the correlation between indexes, risk classification and sequence of different pipe sections are given. The pipeline risk assessment method based on principle component-clustering analysis can improve the reliability and practicality of oil/gas pipeline risk assessment system, and has practical significance for the operation and maintenance of oil/gas pipeline.