The invention relates to a variable pressure distillation method for extracting pythoncidere and essential oil from Chamaecyparis plants. The pythoncidere is aqueous solution, and contains main effective ingredients including borneol, cedrol, carvacrol, bisabolol, and the like. The essential oil from Chamaecyparis plants is yellow and contains cedrene, thujopsene, cedrol, and the like. The variable pressure distillation process comprises the following steps: drying and pulverizing rhizomes of Chamaecyparis obtusa and Chamaecyparis formosensis, filling into a distillation tank, introducing steam from lower steam inlet of the distillation tank for 30-50 s, starting an oil pump to vacuumize so as to generate negative pressure of 40-60 kpa, reducing pressure and humidifying after pressure stabilizes, gradually restoring the negative pressure to normal atmospheric pressure after 20-30 min, connecting a coiled condenser for condensing vapor after 20-30 min, decolorizing with about 50-100 g activated carbon, separating oil phase and water phase, and filtering to remove impurities with filter screen to obtain the essential oil and hydrosol from Chamaecyparis plants, namely, water-soluble pythoncidere.