A novel neutron shielding B4C/CF/PI/AA6061 composite laminate (NSCL) with different layups containing 10 to 50 wt% of boron carbide (B4C) particles was successfully fabricated using a hot molding process. The effects of different B4C loadings and various configurations on the neutron transmission of the NSCLs were evaluated correspondingly. The MCNP 5.0 program was used to probe the neutron transmission mechanism of the NSCLs. The results showed that B4C particles are an effective absorbent, and neutron transmission of the NSCLs decreased with the increment of layups, B4C loadings, and the laminate thickness. Fast neutrons emitted from a 241Am-Be neutron source were first moderated by low atomic elements (hydrogen) and then absorbed by 10B nuclide contained in the B4C particles. Numerical simulation corroborated the experimental testing results.