|In vehicle driving safety, the friction coefficient is the important factor in deciding braking distance. The road friction coefficient manifests non-Gaussian states. In this paper, we use a particle filter, which is a simulation-based approach and which approximates the posterior Probability Density Function (PDF), to estimate the road friction coefficient. We derive the equation of the friction coefficient from the Free Body Diagram (FBD) of the vehicle. Using this equation, we find the μ-slip curve for each different road condition. Through the μ-slip curve, we can determine the road friction coefficient by interpolation. We perform the simulation by Carsim, and the result shows that the particle filter tracks the friction coefficient more accurately than before.