Abstract: To analyze inhomogeneity of density distributions in different areas of public buses,characteristics of standing density of passenger flow is studied through a investigation of 7 crowded bus routes in both off-peak hours and peak hours.Based on different layouts of seats,causes of inhomogeneity,distribution characteristics,and correlation within each other are analyzed.The parts have maximum standing density in each feature interval are verified.Tendency of passengers to choose standing areas are analyzed.The results show that,after get on a bus passengers firstly choose to settle down in area B or C,the possibility is 93.23%.When the average standing density ρin a bus exceeds 6 persons per m2,the maximum of standing density is in area B and C,as the layouts of seats are"1+1 on wheelbase,1+1 on posteri-or passage"or"1+1 on wheelbase,2+2 on posterior passage".When ρranges from 0 to 2 persons per meter2,propor-tion of standing density in area C decreases significantly.When it reaches 40%,the decrease tends to slow dow n.