Unclear puffing power has always been an important problem for instant pressure drop puffing process using superheated vapor. And the condensation water produced by superheated vapor is absorbed by the food material before puffing, which possibly makes bad effect on puffing ratio．A general mathematical model of puffing power was established．Results indicated that puffing energy was produced by flash evaporation of superheated water from internal material and instant release of superheated vapor．Besides，porosity of sample varied with different sample moisture contents and condensation water generated in thermal transfer process before puffing．Thus，puffing ratio was related to the sample moisture content，porosity and status of superheated vapor．Using Granny Smith green apple slice as experimental objects，results suggested that porosity of sample was significantly decreased with the increase of sample moisture content．At temperature of 430～470K，pressure of 0.1～0.5MPa and apple moisture content of 15%～35%，the established puffing power model could effectively predict and evaluate the relationship between puffing condition and puffing ratio (R＞0.89)．High vapor pressure had insignificant influence on condensation water，and distinctively elevated the energy of superheated water and superheated vapor，which resulted in the biggest puffing ratio．High temperature of superheated vapor can only strengthen superheated water energy，but significant increase of condensation water mass led to superheated vapor energy reduction，and it had slight effects on puffing energy improvement and puffing effect．Moreover，high moisture content of sample significantly increased superheated water energy，but condensation water reduced superheated vapor energy，which generally showed great effects on improvement of puffing power and puffing ratio．The research results illustrated the power mechanism of instant pressure drop puffing process using superheated vapor，which would be helpful to further study on the control of puffing ratio.