In China, most of the nickel sulphide deposit is spatially related to ultrabasic rocks and the cementation filling method is used in the process of mining. However, the cement filling from the mine back fill often gets into the ore and interferes with the pentlandite flotation. In this work, the effect of the cement filling on the flotation performance of a nickel ore was studied and ammonium sulphate was used to eliminate this adverse effect. The flotation result shows that the pentlandite recovery decreased from 87% to 65% with the increase of the content of cement filling from 0% to 8%. The addition of ammonium sulphate was shown to improve the flotation performance of pentlandite that depressed by cement filling. This result points out a problem often encounter in the flotation of a nickel sulphide ore and finds a solution to it. (C) 2014 Elsevier Ltd. All rights reserved.