Abstract: Aiming at the beam-wave interaction in the helix TWTA, some of the main calculation results which were based on the loss transmission line model and kinetics equation with the particle-in-cell technic in the time domain were shown in the paper. Comparison of the software which has been released, it is apparent to see the two results were consistent. Later the analysis for the difference of the two models and the difference of calculations were given. These research will be the important foundation of the next work.