Online social networking services allow people to initialize various kinds of offline social events (e.g., cocktail parties, group buying, and study groups), and invite friends or strangers to participate the events in either manual or collaborative manners. However, such invitation manners are tediously long, and irrelevant, uninterested and even spammers can unexpectedly be added into the event. In this paper, we aim at investigating the characteristics of social events participants for a specific organizer. Specifically, we are wondering how social network, user profiles and geo-locations affect user participation when the social event is held by a single organizer. An extensive analysis has been conducted on the real-world event-based social network Meetup dataset. The results of data analysis also demonstrate that these factors actually influence users' event participation.