Abstract: In this paper, the new measuring system, including the Acoustic Doppler Velocimeter (ADV) technique, the plane laser induced fluorescence (PLIF) technique and the laboratory virtual instrument (Labview) technique, are employed to measure the quantitative time averaged and turbulent velocity fields and the scalar concentration fields of a round jet issuing into a co-flowing current.The spreading and mixing characteristics of a round jet in a co-flow are discussed and compared with the works done before.The experimental results show that the radial distributions of dimensionless mean excess velocity, concentration and turbulent intensity at the different downstream location are self similar and the distributions of velocity and concentration are overlapping to the Gaussian curve.The jet centerline velocity decays along with downstream distance increasing and follows different laws in the strong and weak jet region.