Peptic ulcer is an important public health problem affecting about 10% of the world's population. The treatment of this disease is usually long, expensive and less accessibility and affordability of the modern medications by the poor local population. Peptic ulcer represents about 31.65% of cases of consultation in the gastroenterology services in Cameroon. The constraints to have medication have diverted poor patients to rely on traditional medicine for their health problems. The objective of this study was to identify the major classes of secondary metabolites to evaluate in vivo the anti-ulcer activity of the aqueous extracts of Ficus. thonningii on Wistar rats. The experimental model used to induce the gastric ulcers was absolute ethanol 100%. Thirty rats were used for the preventive and curative activity respectively represented in six groups: one group without treatment, three pretreated groups with the extract at (125, 250 and 500 mg/kg), a group receiving a pretreatment with the reference drug omeprazole (20 mg/kg) and another receiving a pretreatment with distilled water (control). Antacid activity was investigated through the determination of the FDA minimal buffer capacity. The phytochemical screening of the extract of the bark showed the presence of the saponins, quinones, coumarins, catechic tannins, phlobotanins, anthocyanin, polyphenols, flavonoïds and betacyanes. Investigation of the in vitro antacid activity of F. thonningii Blume stem bark hydro-ethanolic extract showed that the plant did not possess antacid activity with a 1.18 ± 0.11 minimum buffer capacities after 10 minutes of exposure. In the preventive anti-ulcer study, the percentage protection of the mucous membrane was of 29.80% with 125 mg/kg, 44.27% with 250 mg/kg and 81.18% with 500 mg/kg. This study showed that the hydroethanolic extract of the mixture of the dried bark of Ficus thonningii Blume had a promising gastro-protective activity both preventively and curatively and at 500 mg/kg. The administration of this extract at concentration up to 2000 mg/kg could have a potential effect of vascular protection and hepatic protection.