|The proportion of the elderpopulation in many countries rises because of the technology and medical progress inrecent years. Keeping frequent exercise is the only way for the elderly to live with health and dignity. Lots of the senior citizen suffer from degenerative arthritis and thus, the injury within incorrect posture due to gravityoccurs more in land sports. Water aerobics is therefore more recommended by doctors and been proved effectiveness for the elderly to promote one's own physical and mental health in many researches. In comparison with other sport, water aerobics takes lighter burden. To increase the effectiveness of exercise, the research investigates the causes encouraging people continuously engage in activities. Through the study, we found out the cause is derived from the pleasure of the event and significantly associated with self-satisfaction. The literature review includes the forming of pleasure, the characteristics of pleasure product design, physical and mental function features of the product for the senior citizen and design guidelines of international standards (ISO/IEC guide 71)and so on. Along with the reference of existing available aquatic assist device, we conclude the design guidelinesof aquatic assist device for the senior citizen as follows: (1) Feedback of effectiveness, (2) Easy operation and flexibility in adjusting exercise resistance, (3) Convenience in movability Thisis a User-centered Design.In which to validate design features and user requirements by using focus groups and indirect observation;In order to empirical concepts and design principles that participated the designcompetitions far and wide. In summary, it was confirmed that this point can be used as reference material in the future engage in elderly aquatic aerobics related assist devices. Thus to improve the elderly engaged in the ongoing movement to slow the degradation of the physiological function and promote healthy elderly person's physical and mental functioning.