Weed is a major factor affecting rice yield and quality， and breeding herbicide-resistant rice varieties is an effective approach for weed control. Mesotrione is a 4-hydroxyphenylpyruvate dioxygenase -inhibiting herbicide with great application potential because of its broad-spectrum weed-control， safety to succeeding crops， and the low likelihood of resistance development in weeds. Natural alleles conferring mesotrione resistance are present in rice germplasm resources. This study first employed a liquid culture-based evaluation method to determine 0.2 μmol/L mesotrione as the screening concentration for extremely sensitive materials and 0.8 μmol/L mesotrione as the screening concentration for resistant materials. Then， based on the resistance response of different rice germplasm resources to mesotrione， resistance was classified into levels 1， 3， 5， 7， and 9. Among 760 rice germplasm resources， 19 extremely sensitive germplasm with resistance level 9 were selected using 0.2 μmol/L mesotrione concentration. And then the mesotrione concentration was increased to 0.8 μmol/L， four highly resistant germplasm with resistance level 1 and 28 moderately resistant germplasm with resistance level 3 from the 760 germplasm resources were selected. Further field spraying experiments at the seedling and tillering stages showed that the highly resistant germplasm screened in this study could tolerate up to 80 mL/667 m2 of 15% mesotrione suspension concentrate spray in field test. The liquid culture mesotrione resistance identification method established in this study enable rapid and large-scale evaluation of mesotrione resistance in rice germplasm resources. The highly resistant and highly susceptible germplasm identified in this study not only provide excellent genetic resources for breeding new mesotrione-resistant rice varieties， but also offer important materials for resistance gene mining and genetic mechanism analysis.