Objective To establish an easy, rapid and sensitive method for determination of micro 2,4-dinitrotoluene in waste water. Methods Based on the fact that micro 2,4-dinitrotoluene could inhibit the discoloring oxidation reaction of methylene blue by KIO4 in the HC1 solution, micro 2,4-dinitrotoluene was determined using kinetic spectrophotometric method. Results A new kinetic spectrophotometric method for determination of micro 2,4-dinitrotoluene was established. The linear range of the method was 0.20?10~(-5)-1.8?10~(-5) mg/L, the detection limit was 1.7xlO'7 mg/L. When the method was applied to the determination of the 2,4-dinitrotoluene in waste water, its recovery rates in standard addition method were 95.6%-99.1% and the RSDs were 1.5%-2.6%. Conclusion The method was easier to operate and more rapid, which was suitable for the determination of micro 2,4-dinitrtoluene in wastewater.