Abstract: Effect of a microemulsion composed of sodium dodecyl sulfate (SDS),n-butanol,n-heptane and water on the color reaction of Cr(Ⅵ) with diphenylcarbazide (DPC) was studied and its reaction conditions were optimized by the method of orthogonal design. As shown by the experimental results,highest sensitivity was obtained when the color reaction was carried out in the presence of the above mentioned microemulsion,giving a molar absorptivity of (ε545) 8.07×104L·mol-1·cm-1,which was larger than the molar absorptivity of the same color reaction in common water medium (ε545=4.06×104L·mol-1·cm-1),and in SDS-H2O medium (ε545=3.97×104L·mol-1·cm-1). In its application to the determination of chromium(Ⅵ) in lacquer samples,an average recovery of 97.2% was obtained.