The olivine-type lanthanum and magnesium doped Li0.99La0.01Fe0.9Mg0.1PO4/carbon aerogel composite is synthesized via a simple solution impregnation process using carbon aerogel (CA) as templates, characterized by XRD, SEM, EDS, HR-TEM, galvanostastic charge/discharge test and EIS. The Rietveid refinement results of lattice parameters of the samples indicate that the La3+ and Mg2+ have been successfully doped into the phospho-olivine structure without destroying the crystal structure. The composite has uniform particle size and porous structure, which is believed to be beneficial to its electronic conductivity. It is noted that the capacitance is higher under lower discharging rates at −20°C, and the specific capacity of 1C, 10C, 20C and 50C are 120.3mAhg−1, 85.4mAhg−1, 75.3mAhg−1 and 56.6mAhg−1. The results indicate that both ions doping and carbon aerogel coating are effective way to improve the electrochemical performance of the composite at low temperature and high rate for lithium batteries.