This Book mainly discussed about the field parameters of microwave LINAC(Linear Accelerator cavity)field parameters,its simply a particle accelerator,which we are using mainly in the cancer therapy,NDT(Non-destructive testing) and rocket propellent.Here in this book our main aim is how the electric field is changing inside a single cavity and where we are getting maximum acceleration in side the cavity.To know this parameters we used HFSS(High Frequency Structure Simulator)full wave simulator which is basically operating on FEM(Finite Element Method). Same thing we tried to verify those parameters Computationally.