Pechini　method　was　used　to　prepare　the　nano-phased　active　oxides,　in　which　RuO2,　IrO2　and　PdO　were　the　main　components.　Mono-phased　oxides　can　be　obtained　when　suitable　temperatures　are　selected.　Heat　treatment　has　great　effects　on　crystal　size　of　RuO2,　IrO2　and　PdO.　Though　the　size　increases　with　temperature,　there　is　not　a　simple　incremental　relationship　between　the　temperature　and　the　crystal　size.　The　two-staged　increment　in　the　preparing　processes　is　observed　for　the　three　active　oxides　during　heat　treatment.　The　crystal　size　grows　up　rapidly　at　temperature　lower　than　Tc,　which　is　the　intersection　temperature　between　the　two-staged　increment　lines,　and　grows　up　slowly　at　temperature　higher　than　Tc.　It　implies　that　the　two-staged　increment　of　crystal　size　with　increase　of　temperature　is　a　special　phenomenon　for　precious　element　systems.　According　to　the　two-staged　phenomena,　it　is　suggested　that　the　equation　D=bT+a,　in　which　the　constants　are　obtained　by　curve　fitting　based　on　experiment,　is　helpful　in　the　industrial　processes　to　control　the　sizes　of　the　three　active　oxides.