In this paper, we consider a fractional Sturm-Liouville equation of the form, , cD,0+ ,D,0+y(t) + q(t)y(t) = , y(t),0 < ,< 1,t 2 [0,1],with Dirichlet boundary conditions I1, ,0+ y(t)jt=0 = 0,and I1, ,0+ y(t)jt=1 = 0,where, the sign ,is composition of two operators and q 2 L2(0,1), is a real-valued potential function. We use a recursive METHOD based on Picard's SUCCESSIVE METHOD to , nd the solution of this problem. We prove the METHOD is convergent and show that the eigenvalues are obtained from the zeros of the Mittag-Le, er function and its derivatives.