RuO2　serves　as　a　promising　material　in　electrochemistry　and　heterogeneous　catalysis.　It　has　a　more　outstanding　behavior　than　metallic　Ru.　Nano-scale　RuO2　and　Ru　was　prepared　using　commercial　RuCl3　and　citric　acid　as　source　materials.　The　phase　evolution,　phase　structures　and　crystal　sizes　of　the　derived　products　were　analyzed　by　DTA　and　XRD　techniques.　The　mixture　of　RuO2　and　Ru　was　observed.　The　forming　of　Ru　was　attributed　to　the　disproportionation　reaction　in　solutions　and　the　following　redox　reaction　of　RuO2　in　solid　condition.　Upon　heating,　RuO2　can　be　easily　reduced　to　metallic　Ru　if　the　reactive　atmosphere　possessed　free　carbon　which　came　from　the　incomplete　combustion　of　residual　organic　compound.