The redistribution of physical factors and its impacts on the intensity of squall lines under the influence of low-level Vertical Wind Shear (VWS) and moisture content are examined through two-dimensional idealized simulations with the ARPS model (the University of Oklahoma's Advanced Research Prediction System). It shows that the redistribution of momentum, heat and moisture during the evolution of squall lines leads to the change of inner vertical circulation and the configuration of perturbation temperature and humidity, which affects the organization of deep convection and the intensity of the system. The results of sensitivity tests of low-level VWS and moisture content show that increasing (decreasing) the low-level VWS decelerates (accelerates) the propagation of the squall line, and makes the connection (separation) between the mid-level upward current and the new forced updrafts at the front edge of the cold pool, which corresponds to the intensification (weakening) of the squall line. On the other hand, increasing (decreasing) the low-level moisture content results in an increase (decrease) of moisture delivery from the low to middle level, which enhances (weakens) the mid-level latent heating and upward movement. Energy analysis indicates that the low-level moisture change influences the release of Convective Available Potential Energy (CAPE), and the intensity of the new convection. The combined effects of latent heating and CAPE released from low-level moisture change also affect the squall line intensity through exerting an influence on the organization of the upper-level upward currents and the new forced updrafts at the front edge of the cold pool.