The nucleation and coagulation of nanoparticles in the binary system of water vapor (relative humidity 70%) and sulfuric acid vapor (5×10-6) were detailedly studied by performing numerical simulation in a planar jet (Re=8300). The large eddy simulation was utilized to calculate the flow field, and the particle field is obtained by using the direct quadrature method of moment to solve the particle general dynamic equation. The distributions of particle number concentration, volume concentration and average diameter were discussed. The result shows that the growth of the calculated momentum thickness is consistent with the previous experimental data. The interface of the jet will roll up and generate the coherent vortices which will lead to an obvious decrease of the specie concentration of sulfuric acid vapor and increase of number concentration of nanoparticles in the vortex core. The appearance of the coherent vortices increases the possibility of particle collision and enhances the particle coagulation. The nanoparticle nucleation is enhanced in the vortex core where high particle number concentration will accelerate the particle coagulation.