The present studying is aimed to establish the relationship between flame chemiluminescence$(OH^*,;CH^*,;C_2^*)$ intensities and combustion conditions such as $NO_x$ emission characteristics. Measurements are made for $OH^*,;CH^*,;C_2^*$ radicals in gas & light oil diffusion flames. At turbulent nonpremixed combustion mode, the equivalence ratio is varied. The optical emissions were measured by photomultiplier(PMT) using optical band pass filter and spectrometer system. The experimental results showed that the ratio of radicals and $NO_x$ emission characteristics have exponential correlations and equivalence ratio characteristics have linear correlations at this experimental conditions.