Abstract: A computer program is rewritten based on LINE-ACC/PC and combined simplex searching method and nonlinear leastsquares algorithms in order to accomplish physical design of an X-band 2 MeV traveling wave(TW) electron linac accelerator tube. The time of designing accelerator tube can effectively be shortened. The optimization displayed in the paper can be applied to design of accelerator tubes with constantphase velocity period structure. Calculations of longitudinal particle dynamics, structure parameters and working character also are carried out and demonstrated.