The lymphedema often happens after breast cancer therapy and brings patients great discomfort in their daily life. Therefore, measuring, tracking, and recording becomes a serious clinical issue, but there are still no standard definition and measuring method for lymphedema. The water displacement and circumference tape measurement are mostly used to date. But there are some disadvantages of these methods and influence the difficulty and the accuracy. Thus, the device would be developed according to the conditions relative to disadvantages of these two existing methods. To achieve the conditions, the rotary encoder and grating has been rearranged and tested to develop a new measuring method. The multiple encoder data will be developed and computed as further study in the future.