Based on the conventional lumped parameter circuit model,network equations of piezoelectric transformers (PTs) in parallel-parallel,parallel-series,series-parallel and series-series connection are set up using Y parameter, G parameter, H parameter and Z parameter respectively.All equations are then transformed into Y parameter form,which directly exhibit the relationship between the network characteristics and parameters of single PT and the number of connected PTs.Finally,simulation of electrical characteristics of PTs connected in the four ways is performed,and the theoretical analysis is verified by experiments of parallel-parallel connection.It shows that,only the parallel-parallel connection and parallel-series connection can increase voltage gain and output power.