SrAl2O4:Eu2+,Dy3+ long persistence phosphors are synthesized by combustion method. The effects of several processing conditions such as the mole ratio of urea and metal nitrates, initiating temperature, the amounts of fluxing agent(boric acid), and raw material ratio（Sr:Al）on phase composition and subsequent on the spectroscopic properties are studied. The results show that the phase composition changed from strontium-rich phase to aluminium-rich phase with the increasing of initiating temperature, the increasing of the content of urea and boric acid, and with the decreasing of Sr:Al. The results indicate that the sample has most excellent luminescence performance is not the one which has pure single phase SrAl2O4, but the one has little impurity phase SrAl4O7. Similar phenomenon is also present when synthesized by high temperature solid-state method and microwave plasma synthesis method, so the differences among three methods are also discussed in this paper.