The Mn,Cr-doped and Mn,Cr-co-doped MgAl2O4 powders were synthesized via a gel-solid reaction method at 1400 ℃. A green emission (520 nm) was obtained when Mn-doped sample was excitated at 450 nm. Whilst a red emission (689 nm) was obtained when Cr-doped sample was excitated both at 397 nm and 545 nm as well as a blue emission (450 nm) when excitated at 397 nm. The co-doped Mg1-xAl2(1-y)O4:xMn2+,yCr3+ powders emit green light (515 nm) and red light (677 nm,694 nm ) under pumping at 450 nm. It is found that the energy transfer exists in MgAl2O4 between Mn2+ and Cr3+ in the form of mutual energy accepting and donoring,and the Mn2+ ions have a strong sensitization on Cr3+. Therefore,MgAl2O4:Mn2+,Cr3+ could be used as a phosphor for white LED with blue LED chip. It is proven that the energy transfer in terms of Mn2+ to Cr3+ is by means of radiation and reabsorption.