Cyhalofop-butyl is a selective rice graminicide which can control Echinochloa crus-galli up to the 5-6 leaf stage by foliar application. The development of granule formulations for rice herbicides is important to strengthen agricultural practices in Japan. One granule system of cyhalofop butyl employs KCl core granules and di-tridecyl phthalate to maximize its bioefficacy. This system can enhance plant uptake of the graminicide when a high concentration of cyhalofop butyl + di-tridecyl phthalate comes into direct contact with a plant. The system does, however, limit the flexibility of one shot granule formulations depending on the KCl core granule compatibility with the partner with which it is combined. Therefore, an extruded granule of cyhalofop butyl is preferable to a KCl granule to broaden the potential/possible partners for a one shot granule. Several core granule systems and solvent systems were evaluated to develop an efficacious extruded granule of cyhalofop-butyl. Among them, the employment of a maleic acid polymer type surfactant for the extruded core granule system and di-tridecyl phthalate + isoparaffin as solvent showed the best control efficacy against the 3 leaf stage of E. crus-galli in greenhouse trials than did the KCl granule of cyhalofop-butyl. Granules extruded by this system also showed a high release rate of the graminicide in the upper layer of the water.