: Street space, as a form of public space, accommodates various activities. Jenderal Sudirman Street in Salatiga is an example of a main street downgraded to a lesser classification because it has to accommodate accumulating function and activities. This condition has a direct bearing on the development of the physical Setting of formal activities on the street space. Informal act ivities emerge as a response of space user to the existence of establish formal activity Setting. Predominant commercial function, especially traditional markets, give rise to informal activities in the form of street vendors and its internodes. Limited high-value street space causes conflict among its users. The aim of this research is to formulate types of relationship among formal and informal activity in the street space than describe element which interconnected based on type of relationship . This can be achieved by identifying factors influencing the relationship between behavior of informal activities and formal physical Setting. The method applied by this research is behavioral mapping. This method applies a mapping technique called Placed Centered Map to identify the pattern of various activities happening at an activity node and another mapping technique, Person Centered Map, which identifies the pattern of a street user character dynamically along the street space which function as public space. This method can be used to describe specific human needs at the physical Setting depending on local behavior. Relationship between growing informal an formal activities developing in the same street space will be interconnected an mutually influencing, especially in character, intensity an the physical Setting of street vendors as informal activity. This research has found different types of relationship, interconnected elements and relational pattern between formal and informal activities at Jenderal Sudirman Street, Salatiga. The research focuses on the relationship between traded commodities and the street vendors motivation. In conclusion, four types of relationship were established : same commodity relationship, complementary commodity relationship, neutral commodity relationship and no relation with no street vendors in the area. Elements which interconnected from each type of relationship are fixed element that are pedestrian ways, building character and building set front ; semi fixed elements that are display and drop off area ; and non fixed elements that are pedestrian intensity, speed of vehicle and internodes. This research also found various factors which influence the relationship that are concentric commercial area such as traditional market as main activity nodes, linier commercial area such as shop matters will be attract ed people to walk along the street, access to the building block area, operational time of formal activity, various street users, building physical character and achievable distance for pedestrian.