The radical OH produced in air-aeytilene flame resonantly excited by ultraviolet (UV) laser in 2824～2838A region. The enhanced ionization signals were detected. The spectral bard of radical OH was obtained in the vinicity of UV 2830A, corresponding to a transition of OH X2π→A2Σ(v=0→1). More than twenty spectral line were measured, which oonioide with previous data obtained from flame emmision speotroscopy well. This method has provided a way of radical determination and flame diagnosis.