Background: The rate of population growth in Indonesia are in ranks 108 out of 162 countries. Population and family planning agency of the National has implemented a family planning program (KB) that started since 1970. According to the Population and family planning agency of the National usage pattern trend contraceptives (KB) less rational because of lack of information and education in addition, like to research Olistyawati (2012) the great majority acceptors KB only schedule injecting course. Purpose: This research aims to know the description of the knowledge of family planning acceptor about inject family planning (KB) . Method: This type of research is descriptive research is quantitative with the taking of the sample in simple random sampling with 38 respondents, the research location in Sleman III, Triharjo Sleman. Data retrieval is done by the Division of the questionnaire Results: the results of this research are knowledge of family planning acceptor about type a family planning program (KB) in the knowledge category is average (42.1), the use of time Contraception Hypodermic in the category of less knowledge (73.7%), in indication for injecting a family planning program (KB) categories less knowledge (84.2%), contraindications use of Injection in the a family planning program (KB) category knowledge less (63.2%) and knowledge women in fertile age about the side effects of the use inject contraception in category knowledge lacking (89.5%).