In this paper, an optimized flotation approach, two-stage roughing process, was introduced for improving sphalerite performance based on its mineral liberation characteristics. Mineral Liberation Analysis (MLA), lab-scale and plant-scale flotation tests, and particle size analysis were used to obtain the properties of sphalerite liberation and the particle size distribution. Experimental results showed that the two-stage roughing operation contributed to the sphalerite flotation regarding two aspects: (i) timely pre-separating the well liberated sphalerite to decrease overgrinding; (ii) selectively collecting the poorly liberated zinc minerals for further liberation, which enhanced the regrinding efficiency. Moreover, these advantages were systematically verified from the lab-scale investigation to the plant-scale application. The plant-scale flotation tests showed that the modified two-stage roughing process improved the zinc concentrate grade and zinc recovery by almost 1% and 0.7%, respectively. (C) 2018 Elsevier B.V. All rights reserved.