Lithium is one of the main materials of fuel carrier salt in molten salt reactors. Its neutron cross sections provide an important basic for physical design of molten salt reactor core and for evaluating the safety of the core during operation. The neutron total cross section of natural lithium samples with thicknesses of 8 mm and 15 mm was measured, respectively, in the energy region from 0.4 eV to 20 MeV by using a neutron total cross section spectrometer (NTOX) with transmission method at the Back-n white neutron source of China Spallation Neutron Source (CSNS Back-n) with a 76-m time-of-flight path. High quality experimental data were obtained, especially in the energy region of keV and below. The uncertainty of neutron total cross section is 0.89%~8.5% for the energy region below keV. It provides more abundant and reliable experimental data for nuclear data evaluation of lithium. Additionally, a theoretical analysis was carried out under the guidance of 1/ law and the multilevel R-matrix theory. And the resonance parameters of n%2B6,7Li reaction around energy of 260 keV were extracted from the measured data.