The invention discloses a portable wearable respiration monitoring device and a monitoring method. The monitoring device comprises a flexible respiration monitoring module, a sensing circuit module, a signal processing module and a wearable module. The flexible respiration monitoring module comprises a high-flexibility molecular curing material composed of a hydroxyl-rich natural polymer, a flexible polymer and a metal salt. The flexible respiration monitoring module is fixed below the nostrils of a monitored person through the wearable module, water molecules in gas exhaled by the human body are subjected to adsorption and desorption behaviors on the flexible polymer curing material, and under the action of an electric field, respiration behaviors are generated to respond to electrical parameter changes; the sensing circuit module collects electric signals output by the flexible respiration monitoring module and then outputs the electric signals to the signal processing module, multi-dimensional monitoring of the respiration frequency, the respiration intensity, the expiration and inspiration time ratio, the respiration fluctuation degree, the tidal volume, the abnormal respiration behavior and the like of a wearer is achieved, and the advantages of being accurate and reliable in monitoring result, high in monitoring sensitivity, low in cost and the like are achieved. And the use is convenient.