Abstract: Prestress technology is widely applied in simple beam，continuous beam and continuous rigid frame． Prestressed concrete continuous box girder has big torsion stiffness，big bearing load and good integrality，which is often used for large span，large load and complicated curved bridges． Taking the continuous box girder of Xuankou Bridge as the research object，the theoretical formula deduction，sensitivity analysis and methods of tension control technology were used to study the steel strand tension control stress，elongation and tension control technology． The deduction of theoretical formula shows that tension control elongation is influenced by stretching control stress，length of steel strand，steel strand elastic modulus and embedded pipe etc． Sensitivity analysis shows that tension control stress is the most sensitive factor that affects the prestress． Steel strand tension tests show that elongation error between the measured results and theoretical results can meet the standard，can be reliably applied in the prestressed structure．