The invention discloses a preparation method of a polypyrrole/straw conductive composite material. The preparation method comprises the following steps: firstly washing smashed straws with water, drying the straws, then adding deionized water and a pyrrole monomer, fully stirring to disperse the components, adding an ammonium persulfate solution, carrying out oxidative polymerization to enable polypyrrole to be covered on the surfaces of straw particles, carrying out suction filtering, washing the straws with deionized water, and finally carrying out vacuum drying to obtain the polypyrrole/straw conductive composite material. The polypyrrole/straw conductive composite material can be used as a conductive filler. According to the preparation method, the surface of straw powder is coated with the polypyrrole, so that the prepared conductive filler is extremely high in conductivity; furthermore, the straws are environment-friendly, readily available and relatively low in cost, so that the preparation method is suitable for large-scale production.