Abstract: A magnetic switch based high power long pulse generator was developed, consisting of a pulsed transformer, a low impedance pulse forming network, magnetic core type main switches and an inductive voltage adder. Key subsystems were individually investigated and tested. The pulsed transformer was set up based on magnetic cores with a rectangular cross section and a raceway loop. The two stage magnetic compression system was made via hard connection windings, which were convenient for adjustment. The ceramic capacitor based low impedance pulse forming network was Blumlein type of a circumference symmetrical structure and with magnetic core type main switches cooperated. The inductive voltage adder of 4 stages was developed with each cell feeding by one port via azimuthal transmission line. Furthermore, preliminary experimental researches were carried out on the whole system, which verified the design concept.