Reducing the size of biosignal data is important because a huge amount of data is made by various experiments. In this reported work excitatory postsynaptic potentials (EPSPs) which are one of the biosignal types are efficiently compressed. To the best of authors’ knowledge, EPSPs compression has not been studied yet. The EPSP signal has a feature that the adjacent signals in a single excitatory postsynaptic potential have similar characteristics. Using this feature, a method is proposed which removes the temporal redundancy and statistical redundancy of EPSPs. The compressed and reconstructed EPSPs are similar to the original signal without the loss of analytic information.