This work presented a comprehensive study on structure sensitivity of phase-pure M1 catalyst in oxidative dehydrogenation of ethane (ODHE). We proposed an effective method to modulate the morphology of phase-pure M1 catalysts by oxalic acid treatment. The proposed approach significantly promoted the catalyst surface area by restraining the anisotropic growth of the basal (0 0 1) plane of the M1-phase in calcination and decreased the diameter of M1 needles. Experimental results showed that phase-pure M1 catalyst treated with 1.0 mmol/L, oxalic acid solution exhibited remarkably promoted catalyst performance of 73% ethane conversion, 85% ethylene selectivity and 0.77 k (C2H4)/kg(cat)/h catalyst productivity at 400 degrees C. The serial catalyst tests also demonstrated the structure sensitivity of M1 phase in the ODHE reaction. Active sites were located on the lateral faces as well as the basal plane of the M1 needles, but different effects on the catalyst selectivity were observed. The phase-pure M1 catalyst with a lower aspect ratio was suggested to provide better ethylene selectivity in ODHE process. (C) 2016 Elsevier B.V. All rights reserved.