The present invention discloses a method for pressing dehydration of plant herbarium specimens. The method comprises the following steps: 1) providing an air heater, a shading-cloth sleeve, a specimen clamp, a plurality of newspapers and a plurality of corrugated paper; 2) making a specimen sample; 3) installing the air heater; 4) installing the specimen sample; 5) straight stretching the shading-cloth sleeve; and 6) electrifying the air heater and controlling the baking temperature, wind speed and baking time in the shading-cloth sleeve by adjusting the air heater according to specimen category. After baking is finished, the specimen sample is cooled, the wind speed is kept unchanged in the shading-cloth sleeve, the air heater is adjusted to cool the interior of the shading-cloth sleeve to room temperature, the cooling time is 0.5-1 hour, and then the air heater is shut down and power-off. The method guarantees dehydration is rapid, complete and uniform and the pressed herbarium specimen is smooth.