Abstract: To provide basic comprehension into formation mechanism and spatial distribution of the nano-B₄C_P(n-B₄C_P,50nm), as well as the influence of nano-particle distribution on mechanical properties of 6 vol% n-B₄C_P/2009Al composite. 6 vol% B₄C nanoparticles reinforced 2009Al matrix(6 vol% n-B₄C_P/2009Al) composite was fabricated by efficient 3D mixermulti-stage vacuum hot pressing and hot extrusion method. The results show that, when the ball charge mass ratio is 5:1, B₄C nanoparticles can be distributed uniformly on the surface of Al alloy powders after 30 h milling. The B₄C nanoparticles of 6 vol% n-B₄C_P/2009Al composite in hot pressing state segregate at the matrix boundary, which are uniformly distributed after hot extrusion. During hot extrusion process, the chief mechanism of homogenizing B₄C nanoparticles is that the plastic flow of alloy matrix impose a shear pressure upon B₄C nanoparticles at the matrix boundary and then the cracked B₄C nanoparticles aggregates redistributed along the direction of the shear force. After a solution treatment at 495℃ for 1 h,followed by water quenching and artificial aging at 175℃ for 16 h, the hardness of 6 vol% n-B₄C_P/2009Al composite is 36.4% higher than that of pure 2009Al alloy, and tensile strength and yield strength increase 10.9% and 26.2% respectively. The tensile fracture surface of 6 vol% n-B₄C_P/2009Al composite reveals a mixing characteristic of ductile and brittle fractures.