The precursor solution is sent to the ultrasonic nozzle directly through a needle tube to prepare Zn1-xCrxO（x=0, 0.01, 0.03 and 0.05）films on quartz substratesby ultrasonic spray method.　The structures, optical and magnetic properties of the films were measured by X-ray diffracmeter(XRD), scanning electron microscope(SEM), fluorescence spectrometer, ultraviolet-visible light detector, vibrating　sample　magnetometer (VSM) and so on.　The experimental results indicate that, the undopedZnO thin films exhibit the hexagonal wurtzite crystalline structure with a preferential orientation of (002); the Cr doping restrains the preferred orientation of C axis; the average grain sizes of the samples increase withCr doping, and thesize attains the maximum(31.4 nm) when x=3%. The SEMimages show that the Zn1-xCrxO (x=0, 0.01, 0.03 and 0.05) films are grain-like particles. And it exhibits a long strip shape when x=5%. Moreover, the doping of Cr makes the photoluminescence (PL) spectra of Zn1-xCrxO films change evidently. The undoped sample shows an ultraviolet emission peak at 378 nm as well as a defect related green peak at around 550 nm. However, for the doping samples, there is only a wide range of emission peak from 350 to 550 nm. By gaussian fitting, it is found that VZn, Zni　and　V－Zn defects exist in the Cr doping films, and VZn is largest when x=3%. The band gap increases with the doping of Cr, and reaches the maximum when x=3%. The doping of Cr hasthe band gap of the samples increase, and the band gapreachs themaximum(3.37　eV) when x=3%. Magnetic measured results show that threedoping samples Zn1-xCrxO(x=1%, 3% and 5%) are ferromagnetic at room temperature, and the magnetization of Zn1-xCrxO (x=3%) is the largest, which is corresponding to the most VZn　defect. The experimental results also prove the the oretical prediction that the substitutive Cr in the oxidation state of +3 and the neutral Zn vacancy in the ZnO∶Cr sample are the most favorable defect complex to maintain a high stability of ferromagnetic order.