The notion of the speech community is one of the foci and the main issue of analysis in the ethnography of communication and one of the important concepts in sociolinguistics. In the theory and method of sociolinguistics, it is one of the major problems concerned. Second language acquisition (SLA) is a sub-discipline of applied linguistics and is defined as the learning and adopting of a language that is not your native language as well as the process by which people learn it. SLA is influenced by many factors in a speech community. This paper presents a detailed analysis of speech community; discusses different theories concerning SLA; summarizes the various factors in a speech community which function to influence SLA; and tries to point out the significance of the study and the problems existing in it.