In this paper, an exact solution of Kerr black hole surrounded by a cloud of strings in Rastall gravity is obtained by Newman-Janis algorithm. The influence of the string parameter a0 on the black hole thermodynamics is studied. Furthermore, according to this black hole solution, we investigate the effect of a cloud of strings on gravitational deflection of massive particles. For a receiver and source at infinite distance from the lens object, we use an osculating Riemannian manifold method. While the distance is finite, we apply the generalized Jacobi metric method. For the case between the two situations, the Jacobi-Maupertuis Randers-Finsler metric and Gauss-Bonnet theorem are employed. We find that the expression of angular velocity and entropy of the black hole are the same as Kerr black hole. However, the string parameter a0 has obvious modification on Hawking temperature and the gravitational deflection of massive particles.