In the mineral processing plant of Fenghuangsham copper mine,the Model BFP floatation machine was used and laid out according to the stepped vertical gravity flow pattern,where the middling was returned by pulp pump.A change of middling production makes the floatation targets be very unstable.By the effective and the real time controlling of the middling pumping flow in the floatation cycle,the process of floatation was kept to a relative constancy,hence the goals of improving separating targets and reducing metals loss have been attained.