Aiming at the problem that the existing reverse-closing lock criterion based on the amplitude of residual voltage of voltage-time type feeder automation system may lose effectiveness in cases of two or three phase to ground fault with low transition resistance, a novel method based on the root-mean-square value of transient line-to-line voltage is proposed in this paper to improve the sensitivity of the reverse-closing lock criterion. The residual voltage detection coefficient is defined to evaluate the sensitivity of reverse-closing lock criterion and the blind zone of existing criterion is pointed out. The time window to calculate the root-mean-square value of transient line-to-line voltage is analyzed and the practical setting method of threshold based on the minimum voltage that can ensure the PT is illustrated. PSCAD based simulation and experiments in lab validate the effectiveness of the proposed method. The novel criterion can reduce the number of power outages of opposite side substation caused by the misclosing of the loop switch and it needs not the extra primary instruments, thus its cost is low and convenient to be realized in engineering. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 5226SX1600U9) and Science and Technology Plan of Guangdong Province (No. 2015B010128006).