Abstract: A full scale cold-formed steel OSB composite floor with different boundary conditions was tested to study its vibration behavior. The center deflection of the composite floor under static loading and the fundamental frequency were tested under dynamic loading which includes walking along and transverse to a beam, heel shock, sandbags dropped from the air and hammer impact. Each load case considered four boundary conditions including four sides support and beam end simply supported, four sides support and beam end fixed, two sides support and beam end simply supported, two sides support and beam end fixed. The research showed that changes in boundary conditions would cause changes in the deflection and the fundamental frequency of the composite floor. The vibration performance of the composite floor can be improved through changing the boundary conditions. The maximum deflections were all less than 2mm under 1kN concentrated load and the fundamental frequency was generally greater than 15Hz under dynamic loadings in different boundary conditions. Thus, it is proposed the maximum deflection limit of the cold-formed steel OSB composite floor can be set to 2mm and the fundamental frequency limit can be set to 15Hz when the higher comfort requirement is demanded. The theoretical formulas proposed in this paper which adopted the equivalent stiffness method can be used to predict the deflection under static loads and the fundamental frequency under dynamic loads for the composite floor with different boundary conditions.