Spinel LiMn2O4 powder has been prepared by an auto-ignited combustion of poly(acrylic acid) (PAA)-metal nitrate precursor. The formation route to spinel LiMn2O4 phase from the precursor strongly depends on the mole ratio (MR) of PAA to metal nitrate. The precursors with MR=1.0 and 6.0 directly produced crystalline LiMn2O4 powders by the auto-ignited combustion at very low temperature (200°C), whereas the precursor with MR=3.0 produced Mn3O4, MnO, and carbonate at the auto-ignited combustion stage and formed spinel LiMn2O4 phase after further calcinations at higher temperatures. The obtained LiMn2O4 powders are composed of very fine primary particles (<100nm) but highly agglomerates and have surface area of 14–29m2 g−1.