The invention discloses a device for measuring the bearing capacity of a deep foundation at the bottom of an open caisson and an installation and measurement method of the device. When a first steel shell of the open caisson is assembled, an active earth pressure gauge is installed on a steel shell at the bottom of a corner, then normally pouring concrete inside the steel shell, normally connecting to be high, and enabling the active earth pressure gauge to sink to a certain depth along with the open caisson, and to make direct contact with deep soil; then, applying pressure to an oil cylinderin the active earth pressure gauge by a hydraulic oil pump located outside the open caisson, enabling the oil cylinder and a bottom plate to directly load foundation soil under the action of hydraulic pressure, and monitoring displacement by a displacement sensor, thereby obtaining a Q-s curve of in situ soil and realizing in situ measurement on the bearing capacity of the deep foundation at thebottom of the open caisson.