The invention relates to an automatic assembling device for an O-shaped ring and a check ring in a manual pump, and belongs to the field of mechanical manufacturing. The automatic assembling device comprises a line body portion completing transferring and fixing work of a tray, a straight valve element position alignment portion and an O-shaped ring and check ring assembling portion. The tray connected with a manual pump base is transferred to the O-shaped ring and check ring assembling portion from a previous station through the line body portion and then is fixed; firstly, a straight valve element is subject to position alignment, then after the assembling task of the O-shaped ring is completed, the check ring is assembled, and after being assembled, the O-shaped ring and the check ring are transferred to the next station through the line body; and the line body portion, the straight valve element position alignment portion and the O-shaped ring and check ring assembling portion are connected through a screw. The automatic assembling device has the beneficial effects that the structure is novel, reliability and practicability are achieved, the automation degree is high, the assembling process is reliable and stable, and the device can be directly applied to an automation assembling production line. The labor cost is reduced.