The invention discloses a preparation method for asthma-relieving radix physochlainae watered pills. The method comprises the following steps: (1) grinding radix physochlainae into coarse powder, performing reflux extraction for 1-3 times and 1-4 hours each time by an ethanol aqueous solution with the volume percent concentration of 70%-95% and the mass being 4-10 times that of the coarse powder, combining extract liquid, filtering, recovering ethanol from filter liquor, and concentrating until the relative density is 1.03-1.3 at 65-80 DEG C to obtain concentrated paste; (2) diluting the concentrated paste by purified water according to a mass ratio of 1 to (0.8-1.5), adding ammonia water for alkalizing to adjust the pH value to be 8-11 to obtain alkalized dilute liquid, extracting for 2-4 times by ethyl acetate with the volume being 0.5-3 times that of the alkalized dilute liquid to obtain extract liquor, recovering ethyl acetate, volatilizing in a water bath until no ethyl acetate smell is generated to obtain radix physochlainae extract, drying, grinding, and pressing in a pill making machine to the asthma-relieving radix physochlainae watered pills. The experiment proves that the asthma-relieving radix physochlainae watered pills prepared by the method have a good asthma-relieving effect.