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  easy axes agree with those experimentally observed. The electronic configuration 5f3 was found for all uranium compounds under investigation.