We present ab initio investigation of the electronic structure and magnetic properties of uranium monochal-cogenides: US, USe, UTe. The calculations were performed by using the recently developed LDA+U+SO method in which both Coulomb and spin-orbit interactions have been taken into account in rotationally invariant form. We discuss the problem of choice of the Coulomb interaction value. The calculated [111] easy axes agree with those experimentally observed. The electronic configuration 5f3 was found for all uranium compounds under investigation.