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By using micron α-Si3N4, SiO2, Al2O3 and h-BN as starting materials, O -SiAlON-BN ( Si2-ZAlzO1+zN2-z, z = 0.3) composite was synthesized by reaction sintering. According to theoretical proportion ratio:n(SiO2)/n(α-Si3N4) = 1, the effects of two sintering aid comtosites, Y2O3+B2O3 and Y2O3+TiO2 at 1700℃ for 2h, were studied. The results indicate that Y2O3+TiO2 as sintering aid can accelerate reaction sintering of O-SiAlON-BN more effectively than Y2O3+B2O3, and the relative density of the composites declined with the increase of BN addition (10%, 20% and30% respectively); XRD analysis found that excessive β-Si3N4 existed in the O -SiAlON-BN composite. Therefore, in order to get more pure O -SiAlON and BN phases in the composites ore SiO2 is needed. When Y2O3+TiO2 was used as sintering aid and addition of BN was 10%, the result of cross experiment on condition of A n(SiO2)/n(α-Si3N4) was 1.05, 1.1 and1.2; B addition of sintering aid was 2%, 4% and 6%; C firing temperature was 1600℃, 1650℃ and 1700℃ ;D-soaking time was 1h, 2h and 3h, shows that the sintering properties were influenced by factors of firing temperature, soaking time, addition of sintering aid and n(SiO2)/n(α-Si3N4) in order of importance. In addition, the technical parameter A3B3C3D3 can achieve the highest relative density. Besides, using Pattern Recognition method, the optimized parameter range to form pure O -SiAlON and BN without β-Si3N4 remained was determined as Y ＞ 1024X2 - 230.400X+11.088 ( X =0.9999A-0.0006C-0.0163D, Y =0.0163A +0.0009B -0.0014C+0.9999D).