The invention relates to a platform and a method for rapidly measuring a liquid phase diffusion coefficient D(C) as a function of concentration (C). The core element of the platform is a liquid core cylindrical lens. The liquid core region is a diffusion cell. Lens parameters are selected to reduce the spherical aberration and improve the detection sensitivity of the liquid concentration. A monochromatic collimated light beam forms a dynamic diffusion image on the focal plane thereof after passing through the liquid core cylindrical lens. The method comprises the following steps of: obtainingan experimental concentration distribution function C<e>(x<j>,t<0>) along a diffusion direction according to the diffusion image at time t<0>; solving a diffusion equation by using the diffusion coefficient D<0> under an infinite lean condition as a boundary condition; expanding the D(C) to D(C)=D<0>(1+alpha<1>xC+alpha<2>xC<2>+alpha<3>xC<3>+...); obtaining a calculating concentration distributionfunction C<n>(x<j>,t<0>) at the same moment as C<e>(x<j>,t<0>) after pre-setting a pending coefficient(alpha<1>, alpha<2>, alpha<3>...); comparing C<e>(x<j>,t<0>) and C<n>(x<j>,t<0>); determining D(C)value according to the coefficients [(alpha<1>)<best>, (alpha<2>)<best>, (alpha<3>)<best>] corresponding to the minimum value of the minimum standard deviation between C<e>(x<j>,t<0>) and C<n>(x<j>,t<0>); calculating the concentration distribution C<n>(x<j>,t) at any time (t is not equal to t<0>) according to D(C) and a ray tracing method, and simulating the diffused image; and comparing the experimental and the simulated image to verify the D(C) relationship.