The averaged particle general dynamic equation (APGDE) is derived using Reynolds averaging method. In the APGDE, the coagulation term resulting from the fluctuating concentrations (fluctuating coagulation term, FCT) is modeled based on the turbulent kineticenergy. Then the APGDE is solved numerically using the Taylor-series expansion method of moments in a turbulent jet. Some numerical results are compared with the experiment ones as a validation. Distribution and evolution of aerosol number concentration, mass concentration, mean diameter and geometric standard deviation with and without considering the FCT are given. It is found that the fluctuating coagulation resulting from fluctuating aerosol concentration comes into play at x/D=5 and its function reaches a stable state at x/D=20.The aerosol number concentration, aerosol diameter andgeometric standard deviation with considering the FCT are obviously less, larger and larger than that without considering the FCT. The fluctuating aerosol concentration intensifies the aerosol coagulation, reduces the number concentration and increases the aerosol size. Therefore, the fluctuating aerosol concentration cannot be neglected in the turbulent jet.