Based on strengthened construction technology of lateral tensioning and anchoring carbonfibre reinforced plastic (CFRP) sheet with waveshapedgear, theoretic analysis is made for the losses by material relaxation of CFRP sheet and strengthened member , the losses by temperature changing and the losses by action between screw bolt in waveshapedteeth grip and strengthened member. And prestress loss tests of CFRP after lateral tension are employed for eight members in two types of experiments (four for steel beam pedestal and four for concrete Tbeams strengthening test). Based on test and analysis, a design value of total prestress loss is proposed for CFRP sheet lateral tensioned and anchored by waveshapedgear.