We present an open-source software package WannierTools, a tool for investigation of novel topological materials. This code works in the tight-binding framework, which can be generated by another software package Wannier90 (Mostofi et al., 2008). It can help to classify the topological phase of a given material by calculating the Wilson loop, and can get the surface state spectrum, which is detected by angle resolved photoemission (ARPES) and in scanning tunneling microscopy (STM) experiments. It also identifies positions of Weyl/Dirac points and nodal line structures, calculates the Berry phase around a closed momentum loop and Berry curvature in a part of the Brillouin zone (BZ). Program summary: Program title: WannierTools Program Files doi: http://dx.doi.org/10.17632/ygsmh4hyh6.1 Licensing provisions: GNU General Public Licence 3.0. Programming language: Fortran 90. External routines/libraries used: •BLAS (http://www/netlib.org/blas)•LAPACK (http://www.netlib.org/lapack) Nature of problem: Identifying topological classifications of crystalline systems including insulators, semimetals, metals, and studying the electronic properties of the related slab and ribbon systems. Solution method: Tight-binding method is a good approximation for solid systems. Based on that, Wilson loop is used for topological phase classification. The iterative Green's function is used for obtaining the surface state spectrum.