Single-phase La-1.2(Sr1.4Ca0.4)Mn2O7 has been synthesized from the aqueous solution of metal nitrates and citric acid by the sol-gel technique. Small particle size with high homogeneity of the powder was obtained. The valence of Mn is determined to be 3.45 +/- 0.05 by chemical titration. The MR ratio [rho -rho(H)]/rho(H), is 115% (102 K, 1.5 T) for the composition prepared by the citrate route, and is nearly three times larger than that of the sample prepared by solid state reaction.