A series of experimental studies were made on the effect of amide collectors with different length of carbon-chain on flotation behaviors of hemimorphite,quartz,dolomite and limonite.Meanwhile,the effect of the carbon-chain length on collecting ability of amine had been discussed.The results showed that when pH value of solution is between 9 and 11,there was the best recovery of hemimorphite,the selectivity of amine to hemimorphite is increasing with the increase of the carbon-chain length,octadecylamine has better selectivity and collecting ability to hemimorphite.