A fast sol–gel process that differs in important details from previously reported methods for preparing Li2MnSiO4/C nanocomposite was reported. In the process, hydrochloric acid was used to enhance the hydrolysis of tetraethyl orthosilicate (TEOS) to obtain silanols firstly. And then propylene oxide was added to promote the condensation of the silanols to form a jelly-like SiO2 gel precursor containing lithium and manganese sources in about 3min at room temperature. The final product of Li2MnSiO4/C was obtained by calcining the gel precursor with sucrose. The structure, micro-morphology and electrochemical property of the as-prepared Li2MnSiO4/C nanocomposite were characterized by XRD, TEM, N2 adsorption–desorption, cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). The results indicate that the Li2MnSiO4/C nanocomposite with mesoporous structure is composed of 10–20nm nanoparticles homogenously coated by the carbon. The electrochemical measurements reveal that the initial charge and discharge specific capacities of the prepared Li2MnSiO4/C nanocomposite are 275.2mAhg−1 and 164.2mAhg−1, respectively. After 60cycles, the discharge capacity retention is 80%. The excellent electrochemical performance can be attributed to the nano-sized composites with a mesoporous structure and the in situ surface carbon coating.