Abstract: Based on the 2D finite element model, changes of the fibre distortion region in the preform were investigated during the Z-pinning process. The shape and size of the resin zone were quantitatively characterized. Characteristic parameters of the fibre misalignment angle and the non-uniform distribution of local fibre content were made, and the rule of the fibre non-uniform distribution was obtained. On this basis, influence of the Pin diameter on the microstructure of the laminates was numerically analyzed. The results show that the Pin diameter has a great impact on the resin rich zone. The misalignment angle and fibre volume fraction increase with the Pin diameter, however, the maximum does not change significantly.