Up to present

the design method for TWT is still those founded in the fifties and sixties of this century. In designing the TWT

it usually starts from selecting the value of γa in the range of 1.2-1.6

then calculates the related internal working parameters and the dimensions of the tube until the performances of the tube are satisfied. In such kind of design method

it can not bring the internal working parameters and the dimensions of the TWT in the suitable working region in the first run calculation. It needs the way of cut and try

and has some blindness in mind for a green hand designer.In this paper it gives out a new procedure in the design method. In this new design procedure

it starts from the small signal gain parameter working region diagram（2）

selecting a suitable working region

setting out a working point at the center of the frequency band and obtain the working point value of b

QC and x1

and then calculating the dynamic working curve of the whole frequency band. From this dynamic working curve

we can see clearly on the region diagram whether the working region fixed is satisfied or not. And on this region diagram

we can judge whether there is any possibility of performance improvements of the TWT

and if necessary

see how to move the working point to a better region. Such kind of selection and fixing on the region diagram method makes the designer’s mind clear and avoids blindness.This new procedure can be used for design of small signal gain TWT

of high efficiency and high power tube

and of super wide band TWT.