By mapping the Fock space of many local fermionic modes isomorphically onto a many-qubit space and using the measure of concurrence,this paper studies numerically the mode entanglement of two spinless electrons with on-site interaction U moving in the one-dimensional Harper model.Generally speaking,for electrons in extended regimes (potential parameter λ＜ 2),the spectrum-averaged concurrence N first decreases slowly as λ increases until its local minimum,then increases with λ until its peak at λ = 2,while for electrons in localized regimes (λ＞ 2),Ndecreases drastically as λ increases.The functions of N versus λ are different for electrons in extended and localized regimes.The maximum of Noccurs at the point λ = 2,which is the critical value in the one-dimensional singleparticle Harper model.From these studies it can distinguish extended,localized and critical regimes for the two-particle system.It is also found for the same λ that the interaction U always induce the decreases of concurrence,i.e.,the concurrence can reflect the localization effect due to the interaction.All these provide us a new quantity to understand the localization properties of eigeustates of two interacting particles.