This study examines the factors that may affect the volunteer satisfaction of middle-aged volunteers by constructing an explanatory model. Legal cognition, volunteer service expectations, organization expectations, and job expectations are considered independent variables, with volunteer satisfaction as the dependent variable. The relevant data is analyzed through structural equation models. The subjects of this study are volunteers who live in northern Taiwan and are over the age of 50. A total of 205 valid questionnaires were collected from the subjects. The results show that legal cognition and volunteer service expectations variables will affect volunteer satisfaction, but organizational expectations and job expectations will not. The researchers have put forward conclusions and suggestions accordingly.