Monitoring　of　Beijing　PM10　was　undertaken,　data　collected　in　a　period　of　one　year　showed　seasonal　variation　of　the　mass　level　of　Beijing　PM10　being　highest　in　winter　and　spring,　lower　in　summer　and　lowest　in　autumn.　PIXE　was　used　to　investigate　the　chemical　elements　in　PM10.　Results　showed　the　chemical　concentration　also　varied　seasonally.　Percentage　of　the　masses　of　the　crustal　elements　such　as　Al,　Si,　Mg,　K,　Ca,　Fe,　Mn　and　Ti,　reached　highest　in　spring　and　S,　Cl,　Pb,　As,　Cu,　Ni　and　Zn　which　originated　from　anthropogenic　sources　reached　highest　in　winter.　The　monitoring　data　showed　gradual　increase　of　the　abundance　of　the　elements　from　spring　to　winter　in　Beijing　air　and　especially　strong　correlation　of　Si,　Ca,　Al,　Fe,　Mg　and　Ti　from　the　factor　analysis　indicating　these　elements　coming　from　the　earth　crust　or　soil,　S,　Zn　and　Pb　probably　from　industrial　pollution　and　Cl　and　As　from　combustion.