OBJECTIVE:To identify the optimal intensity and duration of cupping that would minimize mechani-cal skin deformation.METHODS:We developed an optical measurement probe and system for measuring skin color values in real time.We applied cupping at the following five Bladder Meridian acupoints.To investigate opti-mal intensity,negative pressure intensity was in-creased every 2 min up to 80 kPa.To investigate op-timal time,10 measurement sites were selected and negative pressure intensities of 30,60,and 80 kPa were applied for 5 min each.Skin color information was analyzed by the following skin color values:red color saturation,erythema index,and melanin index.RESULTS:The red color saturation and erythema in-dex increased steadily up to 60 kpa negative pres-sure intensity,then decreased between 60 and 80 kPa.Therefore,maximal values were observed at 60 kPa.The melanin index consistently increased with increasing negative pressure intensity.The red col-or saturation and erythema index did not change after 20 s at 60 kPa negative pressure intensity.For negative pressure intensities below 80 kPa,signifi-cant changes in melanin index were not observed after 20 s.At 80 kPa negative pressure intensity,the melanin index exhibited an increasing pattern for 200 s,then showed no changes.CONCLUSIONS.:To minimize skin deformation,60 kPa and 20 s were the appropriate intensity and du-ration when using red color saturation and erythe-ma index as diagnostic indexes.Because of the in-creasing pattern up to 80 kPa negative pressure in-tensity,the optimal intensity of melanin index could not be determined.When applying 80 kPa negative pressure intensity and using melanin in-dex as the diagnostic index,we recommend a dura-tion of 200 s.