Abstract: in order to explare the fotatio behavior f ultr -fine clay and make ful ise of scarce coking cal.the fiotation middlings with49.3% ash content collected fom Cianjiaying Ccal Preparatio Plant and the process o talings discarding by spiral separator integrate with grinding-fatation was caried ou inthe present papet. The resuis showed that the maxinun y eld with 12.5% ash content was cotained when 3.5 min grinding time was adopted.The high ash content concentrated weremainlyatiributed to the ultr - fine clay minerals coating.Acording to the caculaton of iner- paricle potentialfor coa-clay system,two regulation methods were proposed by nodulating the elecrostatic foce or van der Wals force to lower the cay recovery tshould be nofed that the inibiion ofthe clay coatig was contradict with the efiective slime settement.Nevertheless the introdution of nancbuble layer may be the appropriate weay to conrol the clay coating in future becauseof the considerable change of the system Hamaker constant.