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The influence of microstructure on magnetic properties of Sm(Co,Cu,Fe,Zr)z magnets is investigated by micromagnetic finite_element method. The demagnetization curves at different temperatures are also simulated. The calculated results show that the saturation polarization Js depends on the relative proportions of 2∶17 phase and 1∶5 phase. The coercivity and the maximum energy product increase with increasing 2∶17type cell size, while they decrease wi th increasing width of 1∶5type cell boundary. The coercivity analysis shows t hat the magnetization reversa l in Sm(Co,Cu,Fe,Zr)z magnets is mainly controlled by nucleation at cell bounda ry. The abnormal temperature dependence of coercivity is due to the fact that the cell boundary becomes less magnetic even nonmagnetic and the nucleation is difficult with increasing temperature.