The invention discloses an experimental device and an experimental method for detecting OH concentration by utilizing SDBD (Surface Dielectric Barrier Discharge) and emission spectrum and belongs to the technical field of plasma. The experimental device is mainly composed of a circular line-line type SDBD generator (1), a power system (2), an air supply system (3), an ultraviolet source system (4) and an emission spectrum diagnosis system (5). The method comprises the following steps: generating surface dielectric barrier discharge plasma by nanosecond pulses power supply excitation, and detecting the absolute concentration of OH free radical in the plasma by utilizing the ultraviolet source and emission spectrum technology. When the absolute concentration of OH is detected, only the emission spectrum of ultraviolet light is detected, then the emission spectrum of the ultraviolet light passing through a discharge plasma area is detected, and finally, the absolute concentration of OH free radical is calculated. According to the device and method disclosed by the invention, the defects in the traditional technology that the operation is complicated, the equipment is expensive and the like when the absolute concentration of active species is detected can be overcome.