The utility model discloses a jack, which comprises a base, a lifting piece and a tray. At least two supporting pieces are arranged on the base. Each supporting piece comprises an inner rod, an outer rod and a supporting plate. At least two No.1 through holes are uniformly formed in the inner rod. Nuts are fixedly arranged on the No.1 through holes. A No.2 through hole is formed in the outer rod. The No.2 through hole and the No.1 through holes are connected through a screw. The screw is connected with the nuts through threads. The hydraulic jack which is disclosed by the utility model has the advantages that the supporting stability is higher and the safety accidents due to a reason that the lifting piece directly falls off can be avoided.