Abstract: Based on the elastic deformation theory，a mechanical model of composite beam under negative moment was established by considering the surface slip and vertical uplift effects． The differential equation was derived by using the principle of force equilibrium and deformation compatibility condition． Calculation program was developed and obtained the formula of vertical uplift force under negative moment． The results showed that composite beam under same load condition，the uplift force of single stud was increased with the increasing of distance between studs． All the numerical results were verified by comparing with experiment results to illustrate the accuracy and reliability of the calculation method． The result provided a theoretical basis for interface study considering the surface slip and vertical uplift effects of continuous composite beam．