This study was performed to enhance the cleanup efficiency of methoxyfenozide and bentazone by pH adjustment in the course of liquid-liquid partition and to develop an optimum analytical conditions using HPLC coupled with DAD for two matrices, brown rice and rice straw. Preparation procedure of brown rice sample was "extraction${ ightarrow}$coagulation${ ightarrow}$liquid-liquid partition$ ightarrow$-florisil C.C", and this procedure was samely applied to two compounds. In rice straw, preparation procedure of methoxyfenozide sample was "extraction$ ightarrow$-alkalization$ ightarrow$liquid-liquid extraction$ ightarrow$coagulation$ ightarrow$florisil C.C", and in the case of bentazone, "extraction$ ightarrow$alkalization$ ightarrow$liquid-liquid partition$ ightarrow$acidification$ ightarrow$liquid-liquid extraction$ ightarrow$florisil C.C". All these purified samples were redissolved in the mobile phases, acetonitile : 20 mM sodium acetate (75:25, v/v) for methoxyfenozide and acetonitrile : 75 mM sodium acetate, pH 6.0 (40:60, v/v) for bentazone. Recoveries of methoxyfenozide analysis in brown rice and rice straw were 83.5-97.4 and 86.4-97.3%, and detection limits were 0.02 and 0.04 mg/kg, respectively. Recoveries of bentazone in brown rice and rice straw were 86.8-101.9 and 88.3-94.5% and detection limits were 0.005 and 0.01 mg/kg, respectively. This methods seem to be usefully applied to the residue analysis of two compounds in the view of producing stable analytical condition and fair reproducibility.