Abstract: Factor analysis is a multivariate statistical analysis method，which has been widely used in geochemical data processing.The basis of factor analysis is correlation coefficient matrix (or covariance matrix)，which is very vulnerable to data outliers of any kind，and the compositional data closure effect.Therefore， factor analysis in geochemical data processing requires data transformation to obtain accurate results.The geochemical data of stream sediment survey in the east section of Dongkunlun are used to conduct classical factor analysis and robust factor analysis on the raw data，log transformed data and ILR transformed data respectively，aiming to optimize a factor analysis method with better effect in geochemical data processing，make clear the main ores in east section of Dongkunlun and delineate the prospecting target areas.The study results show that the robust factor analysis of the ILR transformed data shows that the main factors have the best correspondence with various genetic type deposits.Based on its factor scores abnormal，seven prospecting target areas are delineated.Four large-sized gold deposits and seven medium-size gold，iron and polymetallic deposits are found in the above prospecting target areas，by further working，some prospecting clues newly obtained in the above areas.In general，the discovered deposits (ore points) are not commensurate with the abnormal size of the above prospecting target areas，and the potential of the further work in the areas is great.

Key words:  Factor analysis, Compositional data, ILR-transformation, Robust analysis, Delineation of prospecting target area, East of Dongkunlun