A new synthetic strategy for high flow nylon 6 was developed in this article. Generation 1, 2, 3 (G1, G2, G3) polyamidomine (PAMAM) dendrimers reacted with p-phthalic acid by equimolar terminal groups in water solution respectively，mother salt solution was then prepared. The high flow nylon 6 was prepared with suitable quantity of mother salt solution, end capping agent (acetic acid), and ε-caprolactam by in situ polymerization. Blue shifts are found for the peaks of NH(γN-H and  2δN-H ) of the high flow nylon 6 compared with pure nylon 6 in the IR spectra. Comparing with the pure nylon 6, the high flow nylon 6 comprises low content of PAMAM units, has high flow property and almost the same mechanical property. The Melt Flow Index (FMI) of the high flow nylon 6 increases (ca. 70-90%), and the tensile strength hardly decrease while the elongation at break decreases (ca. 20-35%). But the izod impact strength of the high flow nylon 6 increases. The SEM images show that the high flow nylon 6 presents brittle fracture with conglomeration-like structure while pure nylon 6 exhibits plastic fracture with island-like structure. DSC thermograms of non-isothermal crystallization exhibit that the peak of high flow nylon 6 broadens comparing with the pure nylon 6, the broader peak means the wider processing temperature.