This paper presents the effect of stray capacitance to the impulse voltage generator.The PSpice program is used to analyze, design and simulate the circuit in both withand without the stray capacitances in different positions of the circuit. From thesimulation, if the stray capacitance is neglected, the output impulse voltage will haveT1 equal 0.36 μs and T2 equal 41.40 μs with the peak voltage at 60.37 kV. If thestray capacitances are added, the values have changed to 0.41 μs, 42.30 μs and59.39 kV respectively. Later, compared the output impulse voltage at different valuesof stray capacitances, it confirms that the output impulse voltage will have T1 and T2were increased whereas the peak voltage were decreased. The results are comparedto the real implementation for analysis and correction. It can be the cause of analyzingand improving the shape of output impulse voltage corresponding to a standardvoltage model in practical.