Due to its high volatility, 210Po can be effectively released from active volcanoes prior to their explosions. A continuous record of the fallout rate of 210Po versus that of 210Pb in northern Taiwan reveals that most of the 210Po was derived from pre-eruption gas emission of Philippines'Mayon volcano in the past two years. From this observation we suggest that, if a global network can be properly designed, it may be possible to employ 210Po anomaly as a precursor of volcano eruptions worldwide.