Djiab, Somia2022-07-042022-07-042022-05http://dspace.univ-msila.dz:8080//xmlui/handle/123456789/29977n this thesis, we have studied four problems of three types of fractional differential equations with integral boundary conditions: ✓ At first, their solutions are presented in form of nonlinear integral equations by using the Green function, which her properties are analyzed to determine the appropriate way to solve the proposed problems. ✓ Secondly, we proved the positivity, existence and uniqueness of solutions to the proposed problems by using some fixed theorems. ✓ Next, we give a new results concerning the stability of fractional equations in Ulam-Hyres sense to prove the stability of solutions for proposed problems. ✓ Finally, several examples are presented to confirm the effectiveness of some utilized theorems.Fractional differential equations, Integral boundary conditions, Fixed point theorems, Ulam-Hyers stabilityThesis