Wettability testing device and method under oil reservoir condition

The invention discloses a wettability testing device and method under an oil reservoir condition. The wettability testing device comprises a high-temperature and high-pressure self-absorption-displacement system, a crude oil circulation metering system and a formation water circulation metering system, wherein the crude oil circulation metering system and the formation water circulation metering system are connected with the high-temperature and high-pressure self-absorption-displacement system; the high-temperature and high-pressure self-absorption-displacement system comprises a nuclear magnetic resonance spectrometer and a high-temperature and high-pressure rock core holder placed in the nuclear magnetic resonance spectrometer; an annular heating system is arranged outside the high-temperature and high-pressure rock core holder; the crude oil circulation metering system and the formation water circulation metering system comprise containers with scales and circulating pumps connected with the containers. A