Many factors affect the electrochemical properties of LiMn2O4. Among these factors the amount of Mn3+ is an important factor which largely influences the capacity and capacity fading. However, it is difficult to detect the amount of Mn3+ by chemical titration method. In this research we try to relate the amount of Mn3+ with the lattice parameter. Lattice parameter is easy to measure. Therefore, if the amount of Mn3+ can be deduced by the lattice parameter, it will be very helpful to control and design the electrochemical properties of LiMn2O4. The results show a good relationship among the lattice parameter, the amount of Mn3+ and the capacity. Thus, lattice parameter could be used to deduce the electrochemical properties of LiMn2O4, although many works are still needed to construct a firm relationship.