This paper presents the design and development of an impulse current generator that can produce impulse current waveform of 8/20 µs. The testing of lightning protection device such as surge arrester is very important to determine this device can be operates in normal condition. Hence, the impulse current generator is developed to carry out the testing because it is clearly not possible to use the actual lightning for the purpose of testing. The first part of this work deals with the calculation of circuit components value followed by the computer simulation to obtain the accurate results. A small scale experimental was set up based on natural characteristics of lightning to study the performance and capability of the designed impulse current generator. This generator is suitable for testing arresters blocks with voltage and current ratings at up 100 kV and 4 kA respectively.