The invention discloses an engine high-compact rocking arm switching device which comprises a cam, a tappet, a rocking arm mechanism and a valve assembly. The outer surface of the cam is provided witha first mold line and a second mold line. The rocking arm mechanism comprises a rocking arm body, a first movable rocking arm matched with the first mold line, and a second movable rocking arm matched with the second mold line. A hydraulic execution mechanism capable of being matched with the upper end portions and the lower end portions of the two movable rocking arms is arranged in the rockingarm body. By controlling the hydraulic execution mechanism, the rocking arms can be switched, the matching rule between the movable rocking arms and the mold lines of the cam is changed, and changingof two and four strokes is achieved. According to the switching device, only one hydraulic execution mechanism is needed, a control mechanism does not need to be operated under each work circulation,instead, adjusting is carried out only under the working condition of needing to change the strokes, the structure is simple, controlling is easy, and engineering application of the changeable valve technology is benefitted.