Adopting a tight-binding electron-phonon interacting model, we investigated the collision between a negative polaron and a triplet exciton in polymers under the influence of different electric fields. The results show that, after the collision, the electrons of the system have the most probability of keeping the same configuration as it initially is. The electron confined in the polaron defect has some probabilities to be excited into the conduction band to form a free carrier， and the triplet exciton has some, even less, probabilities to be annihilated by the negative polaron to form an excited polaron in the collision. It is also found that the collision proccess can influence the stability of the polaron and there are new energy levels appearing in the gap after the collision. Because an excited polaron can decay radiatively to its ground state, the scattering process has influence on the efficiency of electroluminescence. These results will help us to understand the properties of polaron transport and electroluminescence in polymers.