The site occupancy of refractory element W in the (010) edge dislocations of NiAl intermetallic compounds and its effect on NiAl properties are studied by the first-principles discrete variational method. The energetic parameters (binding energy, the impurity segregation energy and the interatomic energy), the density of states and the charge density are calculated respectively for the clean dislocation system and the doped dislocation system. The calculated results of the binding energy and the impurity segregation energy suggest that W exhibits a strong Al site preference. The interactions between the refractory elements W and the neighbouring host atoms are strengthened due mainly to the hybridization of 4d orbital of impurity atom and 3d orbital of host Ni atoms (3p orbital of host Al atom). Meanwhile, some charge accumulations appear between impurity atom and neighbouring host atoms in the dislocation core, indicating that strong bonding states are formed between the impurity atom and its neighbouring host atoms. The refractory element W greatly affects the energy and the electronic structure of NiAl intermetallic compounds, and in turn influences the motion of dislocation and the properties of NiAl compound.