An improved method for preparing melamine cyanurate (MCA) based flame retardant polyamide 6 (FRPA6) materials has been proposed. This processing method, i.e., improved in situ polymerization, was used to synthesize flame retardant PA6. In situ formed MCA nanoparticles were supposed to be linked to PA6 chains in the e-caprolactam hydrolytic polymerization system to obtain star- type polymers for the first time. Through TEM photographs, it can be found that the in situ formed MCA nanoparticles with diametric size of less than 50 nm, are nanoscaled, highly uniformly dispersed in the PA6 matrix. Synthesized ?ame retardant PA6 have good fire performance which can achieve UL-94 V-0 rating at 1.6 mm thickness with the presence of 7.34 wt.% MCA in the matrix. This processing method, ie, improved in situ polymerization, was used to synthesize flame retardant PA6. In situ formed MCA nanoparticles were supposed to be TEM-linked to PA6 chains in the e-caprolactam hydrolytic polymerization system to obtain star-type polymers for the first time. Through TEM photographs, it can be found that the in situ formed MCA nanoparticles with diametric size of less than 50 nm, are nanoscaled PAH has a good fire performance which can achieve UL-94 V-0 rating at 1.6 mm thickness with the presence of 7.34 wt.% MCA in the matrix.