In this paper a simulation using MATLAB for grinding circuit and direct classification, for which the material balance equations arising in the circuit is developed, considering that there are three nodes necessarily the circuit is divided into three subsystems, the first subsystem in the circuit, (S1) is formed by the hydrocyclone and the the second subsystem (S2) is formed by joining two streams fresh feed and the hydrocyclone underflow, the third subsystem (S3) is formed by the mill. Because the feed to the mill depends on the discharge of the hydrocyclone feed to the hydrocyclone and depends on the mill discharge therefore is solved iteratively by the method of fixed point, the variable which is iterated is circulating load, for start the simulation must enter the dimensions of the equipment with operating conditions plus an initial value for the circulating load, once achieved conve...