In order to determine the fermentation period during which the traditional soybean paste possesses the best aroma quality,aroma components in different fermentation periods of traditional fermented soybean paste in Northeast region were extracted by headspace solid phase micro-extraction( HS-SPME),and analyzed by gas chromatography-mass spectroscopy( GC-MS) when p-methoxybenzaldehyde was used as internal standards in semi-quantitative analysis. Factor analysis was used to construct the model of aroma quality evaluation of soybean paste and comprehensive scores were used as evaluation indexes. Results showed that totally 56 volatile compounds in different fermentation periods were identified,including 9 esters,6 alcohols,5 aldehydes,4 ketones,9 acids,9 phenols,7 heterocyclics,5 phenols,and two other compounds. Contents of aroma components in soybean paste changed obviously,on Day 45,content of 8176. 422 ng /g was the highest,along with the fermentation processing,the content of aroma components was on the decline as a whole,on Day 70 and Day 75,the contents of aroma components were 4052. 849 and 2265. 616 ng /g respectively. Three common factors were obtained by factor analysis and named mixed factor,contribution factor and increased aroma factor respectively. Comparison of comprehensive scores of aroma in soybean paste in different fermentation periods showed that score was the highest on Day 45 followed by Day 65 and Day 55,score was lower on Day 70 and 75,so the best fermentation periods was from Day 45 to Day 65.