To improve spinnability of in-situ polymerized solution dope, a low temperature ulitiator Brazobis(2, Ldimethyl valeronitrile)(ADMVN) was utilized in preparing acrylic polymers, and the kinetics of polymerization was described. On the wholes the experimental results well corresponded to the theoretically predicted tendencies. The rate of conversion is generally increased either with increasing initiator and monomer concentrations or with raising polymerization temperature. The inherent viscosity of polymer was decreased with increasing polymerization temperature or initiator concentration but increased with increasing monomer content. In comparison with polyulerization of AN by 25-azobis(isobutyronitrile), the autoacceleration reaction was not so noticeable in the low-temperature polymerization process even at monomer concentrations as high as 30wt%.