NOVELTY - Preparing superfine powder of Angelica sinensis at normal temperature, comprises drying A. sinensis pieces until the moisture content is less than 10%, grinding A. sinensis at 20-25 degrees C to obtain the coarse powder having the granularity of 60-80 meshes, allowing the coarse powder to enter into a special bidirectional airflow screening machine so as to sieve via a 500-mesh unit and by pneumatic conveying after grinding the coarse powder in a rod mill, and conveying the sieved powder until the granularity is not more than 25 microns to a cyclone retainer.    USE - The method is useful for preparing superfine powder of Angelica sinensis, which is useful as feed for animals e.g. poultry. No biological data given.    ADVANTAGE - The method is capable of easily and economically preparing the superfine powder of Angelica sinensis, in a large-scale production, with high efficiency and good quality and without creating any environmental pollution.    DETAILED DESCRIPTION - Preparing superfine powder of Angelica sinensis at normal temperature, comprises drying A. sinensis pieces until the moisture content is less than 10%, grinding A. sinensis at 20-25 degrees C to obtain the coarse powder having the granularity of 60-80 meshes, allowing the coarse powder to enter into a special bidirectional airflow screening machine so as to sieve via a 500-mesh unit and by pneumatic conveying after grinding the coarse powder in a rod mill, conveying the sieved powder until the granularity is not more than 25 microns to a cyclone retainer so as to collect and obtain the superfine powder finished-product via air current produced by a draught fan, and collecting the powder, which is not sieved and then conveying to the rod mill to circularly grind again via a pipe. An INDEPENDENT CLAIM is included for a special bidirectional airflow screening machine comprising a shell (1) and a screen drum (2) with a downward opening in the middle of an inner cavity, where the mesh number of the screen drum is less than 500 meshes, a screen opening of the screen drum is connected with an upper opening of a hopper (3) at a lower part of the shell, an inner cavity of the shell is communicated with a draught fan (5) via an upper negative pressure chamber (4), a door-shaped rotary air ejection pipe constituted by a horizontal pipe and a vertical pipe is arranged in an area between the screen drum and the shell, the air nozzles of the door-shaped rotary air ejection pipe are through grooves, which are axially opened on the pipe walls of the horizontal pipe and the vertical pipe, the through grooves are respectively opened towards a direction of the screen drum, and are 0.5-2 mm wide, while a middle part of the horizontal pipe is connected with a drive motor in a transmission way, a blast pipe is set in the middle of the screen drum, an air outlet of the blast pipe is communicated with a middle part of the horizontal pipe of the door-shaped rotary air ejection pipe in a rolling way via a rolling bearing after passing through the screen drum, an air inlet of the blast pipe is communicated with a blast nozzle of an air blower after extending outside a side wall of the hopper, a feeding pipe is installed in the screen drum, a buffer umbrella is disposed above a discharge hole of the feeding pipe, and the feeding port of the feeding pipe is communicated with an air outlet of a powder conveying fan via an air stopping device after extending outside a side wall of the hopper.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a system for preparing superfine powder of Angelica sinensis.    Shell (1)    Screen drum (2)    Hopper (3)    Pressure chamber (4)    Draught fan. (5)