In this work, melamine cyanurate (MCA) and boehmite (BM) were used to improve the flame retardancy of polyamide 6 (PA6), and a series of BM/MCA/PA6 composites were prepared. The effects of MCA and BM on flame retardancy, combustion and thermal degradation behavior of 15-MCA/PA6 and BM/MCA/PA6 composites were investigated by methods of limited oxygen index (LOI) measurement, vertical burning test, cone calorimeter test and thermogravimetric analysis (TGA). The results showed that MCA can effectively flame retardant PA6. When 15 wt% MCA was added to PA6, composite sample (15-MCA/PA6) possessed LOI value of 30. 4% and V0 rating (3. 2 mm) in UL-94 test. By replacing part of MCA with BM, with an increase of BM amount, the flame retardancy of BM/MCA/PA6 composite was better at first, but then got worse, and mechanical properties were increased. The flame retardancy, thermal stability and combustion behavior data of 4-BM/11-MCA/PA6 composite were better than 15-MCA/PA6 composite, indicated that appropriate amounts of MCA and BM in PA6 had synergistic flame-retardant effects. The time to ignition (TTI), the peak of heat release rate (PHRR), total heat rate (THR), total smoke release /total mass loss (TSR/TML) and fire performance index (FPI) of 4-BM/11-MCA/PA6 composite were 53 s, 322. 5 KW. m−, 2, 79. 8 MJ. m−, 2, 98. 3 g−, 1 and 0. 16 s. m2. kw−, 1, respectively. The LOI value of 4-BM/11-MCA/PA6 composite was 33. 8% with V0 rating (2. 0 mm) in UL-94 test.