The invention discloses a liquid cooling device of battery set, comprising a radiator between batteries in battery set and a radiator block outside the battery set, wherein one duct module is respectively communicated with the two ends of the radiator and one input output end of the radiator module is respectively communicated with another end of the duct module. The liquid cooling device can quickly and effectively take away the heat in battery set, thereby making the user of the battery set more reliably and stable, and the service life of the battery set in prolonged.