Recently, a market of architecture is requiring buildings of long spanned structures as most buildings become taller and larger. For being long spanned structures, elements of buildings must be light. As an alternative proposal, various hollow-core slabs and flat plate salbs were developed and used frequently in the inside and outside of the country. But the study of the hollow-core slabs using deck plate and assembly of light weight is the first. In the present study, Flexural and vibration tests were performed on the hollow-core slabs using deck plate and assembly of light weight to investigate the flexural behavior and serviceability. Four test specimens were used for test parameters; one hollow-core slab with an assembly of light weight, and three hollow-core slabs with deck plate and an assembly of light weight. The test parameters also included amount of tension bar and existence of shear reinforcement. The test results showed that the hollow-core slabs with deck plate and an assembly of light weight had a crack of shear, so shear reinforcement must be conducted.