In order to restrain or prevent AN phase transition,six kinds of polymers were added to AN samples and the effects of polymers on AN phase transition were studied by differential scanning calorimetry (DSC) method. The results show that sodium p-ethylene benzenesulfonate-acrylic acid polymer has little effect on AN phase transition,while sodium p-ethylenebenzene sulfonate-dodecyl acrylate polymer prevents the transition of Ⅳ-Ⅲ effectively. And sodium p-ethylene benzenesulfonate polymer,dodecyl acrylate,sodium p-ethylenebenzenesulfonate-N,N-dimethyldiallyl ammonia chloride polymer and sodium p-ethylenebenzenesulfonate-dodecyl acrylate-N,N-dimethyldiallyl ammonia chloride polymer prevent the transition of Ⅲ-Ⅱ effectively. The effect of polymer on AN phase transition results from that polymer strengthens the hydrogen-bond network and baffle the turn of NO₃^-.