Dielectric barrier discharge (DBD), a method for generating low-temperature plasma, has been widely utilized across various fields. Due to variations in factors such as electrode structure and excitation source, the low-temperature plasma produced by discharge exhibits diverse characteristics, including the type, intensity, and distribution of active particles. Among these, the concentration and distribution of active particles play a crucial role in applying low-temperature plasma. This study aims to investigate the spatial distribution of active particles in the plasma region generated by the discharge. It proposes a diagnostic method for assessing the spatial distribution of active particle concentration, based on ultraviolet spectral imaging technology. Utilizing ultraviolet spectral imaging, a corresponding bandpass filter is employed to convert the collected ultraviolet (UV) spectral image into turbo mapping. The image grayscale is then extracted to analyze the spatial distribution of characteristic particle concentration. This study uses N₂ (337.1 nm) active particles, generated by needle-plate DBD discharge driven by pulse power, as an example to analyze their spatial distribution characteristics under varying parameters. The results indicate that, under pulse voltage drive, N₂ (337.1 nm) excited state particles are primarily distributed along the axis of the discharge channel formed by the needle tip structure and begin to diffuse near the dielectric. The deposition electric field, generated by the charge on the surface of the dielectric plate, intensifies the ionization and collision of nearby particles, resulting in deposition on the surface of the dielectric plate as a large area of high concentration. Along the centerline of the discharge channel, the intensity is highest at the needle tip and gradually decreases as the distance increases. Particle concentration increases on the surface of the dielectric. When the voltage reaches a sufficient level, a second intensity peak appears at the head of the channel, primarily due to the high density of high-energy electrons. In the discharge channel, the particle concentration is predominantly centered in the channel's center and rapidly decays towards both sides, forming a clear boundary. As the voltage increases, the boundary becomes more pronounced. Finally, the Bland-Altman plot method was employed to verify that the method proposed in this study is highly consistent with the particle intensity change trend and amplitude reflected by the emission spectrum, validating the accuracy of the ultraviolet spectral imaging detection method, which can aid in subsequent particle regulation and enhance application efficiency.