We often meet the fronting peak in analysis chromatography and preparative liquid chromatography.Because the fronting peak has a very large width, it can bring serious overlap peak and bad separability.In this article, using the non-linear plate theory simulated the fronting peak with the Langmuir and quadratic polynomial isotherm.Also the two isotherms are all concave curve, but they give different shape fronting peaks shape.Langmuir and quadratic polynomial isotherm can be written: Cs=γ1CM/(1+γ2CM) and Cs=γ3 CM+γ4CM^2, where CS is the concentration of a solute in the stationary phase, CM is the solute concentration in the mobile phase, and both γ1 to γ4 are constants which link to the retention time and peak shape respectively.The calculations of result were shown in figure 1 to 4.The number of plate is 200, jumping number is 1000, and total mass (CS+CM) is 1, 5, 10, 25, 50 respectively.γ1 and γ3 are 1, γ2 and γ4 are-1 and 1 respectively (were shown in figure 1 and figure 2), and γ2, γ4 are-3,3 respectively (were shown in figure 3 and figure 4).