The determination method of olive polyphenol hydroxytyrosol in a soft capsule was improved. The determination was carried out by HPLC with UV spectrophotometric detection. The capsule shell was included in the sample preparation. The samples were diluted with acetonitrile and water in an ultrasonic water bath for 60 min. After this, this solution was diluted with methanol again. The recovery was over 95 % and the relative standard deviation was within 3 %. This method allowed for the simultaneous determination of hydroxytyrosol and oleuropein.