The magnetic and dielectric properties of the ferroelectromagnet(FEM) Pb(Fe1／2Nb1／2)O3 (PFN) single crystals have be en investigated.Anoma lies i n the dielectric constant as a function of temperature have been observed near i ts Neltemperature of　～143K，which are indicative of the so-called magnet oelectric coupling between the ferroelectric and antiferromagnetic orders in thi s compound.It is demonstrated that a weak magnetic transition appeared at the te mperature a little below the Nel temperature，which confirms the earlier predi ction from the Monte Carlo simulation in a qualitative sense.The magnetic hyster esis measurement proves that there does exists a weak magnetic order in PFN crys tal below its Nel temperature.