A process for manufacturing a fibrin membrane from blood plasma that was partially depleted and subjected to coagulation by adding a solution of a physiological coagulating agent, leaving the mixture to stay until forming a gelatinous blood clot, and then dehydrating said blood clot to obtain a fibrous membrane, which is subjected to washing with softening agents and then to drying until obtaining a flexible and mouldable membrane. The membrane so obtained is capable to provide an immediate and complete haemostasis, followed by a whole reabsorption, without risk of adhesions with the neighboring tissues, up to the cicatrisation of the injured tissue. The membrane is mouldable and elastic, and is provided with high mechanical properties. It may be soaked with disinfectant agents, drugs or tissue growth factors.