while other 4 factors were fixed,removal rate(%) of caffeine increased with the increase of temperature and reached the maximum value on the range from 60 to 80(45 to 65).Figure 2B shows that,with the increase of the pressure ,the removal rate of caffeine increased,especially on the range of 25 to 30.The removal rate increases with extraction time(Figure 2C).From economic considerations,2 to 4h is appropriate.