Abstract: Immersed moving boundary is one of the important numerical methods for modeling fluid-structure interaction. However, its original weighting function to determine fluid-solid interaction is empirical and its form is fixed, which is difficult to predict complex fluid-structure phenomena accurately and quantitatively. In this study, a new weighting function is proposed to improve the immersed moving boundary in the framework of the lattice Boltzmann method. By assuming that the multi-order derivative of the weighting factor at zero solid volume fraction is 0, an adjustable parameter b is introduced to enhance the correlation between the weighting function and the solid volume fraction, which improves the permeability performance of the solid boundary. The new weighting function is tested against three benchmark cases namely, flow around a stationary cylinder, Taylor-Couette flow, and flow around an oscillating cylinder. Numerical results show that, with the increase of the Reynolds number, the lift-drag coefficients predicted by the original weighting function are higher than the literature results, which seriously underestimates the effect of fluid components at the boundary. In addition, when the parameter b in the new weighting function is 3, the effect of the improved immersed moving boundary is optimal. Furthermore, the new weighting function enhances the permeability of the solid boundary, improves the prediction accuracy of the fluid field, and reduces the averaged error up to 38.5%. Finally, the frequency-locking phenomenon encountered in flow around an oscillating cylinder is successfully reproduced by using the new weighting function, demonstrating the improved immersed moving boundary is promising in dealing with complex fluid-structure interaction problems.