Abstract: One thermal diffusion trial cascade was set up according to the classical thermal diffusion theory, with emphasis on engineering applications. The calculation of the separation factors and the aspects affecting it were discussed, thermal diffusion transfer coefficients which effect the differential equation of thermal diffusion were researched, factors effecting thermal diffusion separation efficiency were analyzed through the equations of transfer coefficient. The solutions of the differential equations were calculated, through which the length of thermal diffusion cascade and the abundance of isotope products were calculated. Main factors about temperature, pressure, velocity of flow, and theory models were studied. On the basis of above, one thermal diffusion cascade was built for separating isotopes ²²Ne and ²⁰Ne. Equilibrium time is 2 weeks for 99.9%²²Ne and 1 week for 99.9% ²²Ne respectively, it runs over 6 months and produces 240 mL/d 99.9%²²Ne and 600 mL /d 99.9%²⁰Ne. It’s proved in practice that the device was highly efficient in enriching isotopes, which will do great value to the design of isotope separation cascades.