This research aims to establish an HPLC method for the simultaneous determination of konjac glucomannan (KGM) and starch in konjac powder. In this paper, konjac powder was hydrolyzed into glucose and mannose by acid hydrolysis. The hydrolysate of konjac powder was derivatized by 1-phenyl-3-methyl-5- pyrazolone (PMP). The contents of glucomannan (KGM) and starch in konjac powder were determined by HPLC with UV detector. The relative standard deviations (RSD) of KGM and starch in four kinds of konjac flour were ≤4.40%, the recovery of glucomannan was 87.98%~103.31%, and the RSD was ≤5.25%; The recovery of starch was 91.50%~108.05%, RSD≤7.67%. This method can be used for the simultaneous determination of KGM and starch in konjac powder. The establishment of this method is of great significance to the classification control of konjac powder.