Insitu ring opening anionic polymerization of Laurolactam towards polyamide 12 (PA12) was successfully performed via the melt polymerization of Laurolactam as monomer in the presence of sodium caprolactam as a catalyst, and toluen diisocyanate as an activator during reactive melt blending. This reaction takes place at a significantly faster rate and gives a narrower molecular-weight distribution than those obtained with other techniques. The effects of various concentrations of catalyst and activator on the rate of reaction and the amount of residual monomer were determined. In order to characterize the synthesized samples, DMTA, TGA and DSC analysis have been done. Also the existence of amide groups was proved by ATR and XRD spectrums accordingly