Abstract: Five unbonded prestressed lattice type steel-reinforced concrete beams and one lattice type steel-reinforced concrete beam were tested. The sectional strain variation, deformation, tendon stress increment development and crack distribution were analyzed further. The results show that applying prestress to a lattice type steel-reinforced concrete beam can improve crack bearing capacity obviously under the same other parameters. The load-deformation curves take the crack of tensile region concrete and the yield of tensile steel lower flange as deviation points and appear a trilinear characteristic. The beam failure modes are compared with those of a non prestressed lattice type steel-reinforced concrete beam, the crack appears late and develops more slowly, and the main crack characteristic is not obvious. The calculation results obtained by using crack and ultimate bearing capacity formulas suggested in this paper are in good agreement with the experiment ones.