Co-precipitation method was employed to synthesize Mn doped ZnO dilution semiconductors Zn1-xMnxO with the nominal composition of x=0.001, 0.005, 0.007 and 0.01. The annealing temperature (Ts＝400,600,700 and 800℃)dependent structure as well as the magnetic property of the produced samples were studied. The results indicated that samples sintered in air under the temperatures of 600℃ has single wurtzite ZnO structure with prominent ferromagnetism at room temperature; while in samples with the Mn nominal content of 0.007 and 0.01 sintered in air at 800℃, a second phase, namely the ZnMnO3 was observed. The sample with x=0.007 shows largest magnetization and coercivity. Increasing the annealing temperature to 800℃ results in decreasing of both magnetization and coercively，and the paramagnetism was enhanced. Combining with the analysis of the PL spectrum, it is reasonably concluded that the ferromagnetism observed in the studied samples originates from the doping of Mn in the lattice of ZnO crystallites.