Both fluorescence dynamics and time-dependent electron transitions are introduced within a previously developed molecule dynamics approach for treating conjugated polymers. This is able to provide a panoramic view of luminescence dynamics during singlet exciton decay, in which the fluorescence dynamics is largely determined by the electron population and the evolution of the dipole moment. The fluorescence intensity is weakened due to a reduced dipole moment and diminished decay rate of the electron, which validates a previous assumption based on experimental studies. The lifetime of the singlet exciton in a conjugated polymer is found to be 1.2 ns, and the calculated time profile of the fluorescence intensity is in agreement with recent experimental results.