The improved Bessel-Legendre inequality is characterized with such an advantage as being easy to deal with in time-varying delay systems, which overcomes the flaws of the integral inequality based on auxiliary functions and the Bessel-Legendre inequality in dealing with time-varying delay systems due to their inverse convexity in the definition of results. A new robust stability criterion for time-delay systems has thus been established by constructing appropriate Lyapunov-Krasovskii functional and applying the improved Bessel-Legendre inequality to deal with the integral terms in the functional derivatives. Finally, a numerical example is given to verify the simulation results, which are then compared with those in the existing literature. The results show that the upper bound of the system maximum allowable time-delay of the proposed method is obviously superior to the results in other literature. It can be seen that the time-delay stability margin of the system has been improved substantially, which further proves the effectiveness and superiority of the proposed method.