Abstract: Study on the motion and dilution of oscillating jet in cross-flow environment is of great importance for sewage discharge engineering. The initial dilution characteristics of an oscillating jet in cross-flow environment were investigated using a three-dimensional large eddy simulation model. The impact of each jet parameter on the initial dilution effect of the jet was discussed. The empirical formula of minimum dilution and the visible area of oscillating jet were identified through dimensional analysis with characteristic velocity and characteristic length. The comparison between the oscillating jet in cross-flow environment and the non-oscillating jet in wave-current environment was also addressed in the study. It suggests that the maximum concentration on the downstream section of the oscillating jet in cross-flow environment occurs either at the position of the counter-rotating vortex pair (CVP) or the "effluent cloud". The larger the oscillating amplitude ratio R_aj, the larger the minimum dilution and the visible area; as S_t decreases, the visible area increases while the minimum dilution does not change significantly. The empirical formula for initial dilution of the oscillating jet in cross-flow environment have the same structure with those of non-oscillating jet in the wave-current environment, and the initial dilution promotion induced by jet oscillation is similar to the wave effect.