The work aims to develop a novel flux-cored wire with La2O3 for hardfacing armored car crawler belt and improve wear resistance of the hardfacing alloy layer by refining the microstructure. The hardfacing alloy layers were deposited by means of automatic open arc surfacing welding method. The microstructure was observed by using an optical microscopy. Meanwhile, Rockwell hardness and wear resistance of the hardfacing alloy surface were measured. The microstructure of the hardfacing alloy contained bainite, martensite and residual austenite. The average size of primary austenite was about 42 μm and mass loss of the La2O3-free alloy 6000 min/g. With La2O3 added, the average size of primary austenite was about 36 μm and mass loss 12300 min/g. The two-dimensional lattice misfit between the (001) face of LaAlO3 and (100) face of austenite was 3.81%. With La2O3, LaAlO3 as most effective γ-Fe heterogeneous nuclei, the primary austenite is refined and thereby the wear resistance of the hardfacing alloy layer can be improved as well.