The invention relates to the technical field of operation, maintenance and monitoring of substation direct-current systems, and in particular relates to a method for judging whether a storage batteryis separated from a direct-current bus or not. The method in the invention comprises the steps of: monitoring the voltage of the direct-current bus, the voltage of the storage battery and the monomervoltage of each battery of the storage battery in real time; and, according to a voltage difference value obtained by calculation, judging whether the storage battery is separated from the bus or not,and judging a separation reason. Due to comprehensive monitoring judgement on the voltage of the bus, the voltage of the storage battery, the monomer voltage of the storage battery, the internal resistance of a monomer and the like, a relatively complete method for judging whether the storage battery is separated from the direct-current bus or not is formed; the method has relatively high security and reliability; and furthermore, the judgement accuracy rate is increased to a certain degree.