Nowadays, nanotechnology has attracted much attention in developing new drug delivery systems. Various nanocarriers with organic, inorganic and organic/inorganic origin used by many researchers. Montmorillonite is one of the most practical inorganic matters which used for delivery of drug and biomolecules. In this study, antibacterial property changes of tetracycline after it desorption in two simulated gastric acid solution with pH=1.2 and intestinal simulated solution with pH=7.4 under two discrete and continuous desorption processes investigated. In addition, the photostability of raw and desorbed tetracycline reviewed in this project. For this propose, three montmorillonite samples which were purified and modified using physical and physical-chemical methods utilized as tetracycline adsorbents. Adsorption of tetracycline on modified montmorillonite studied at three pH of 2.3, 5.4 and 8.4. The XRD analyses showed that the tetracycline diffusion in between montmorillonite layers decrease with increasing absorption pH. According to desorption tests, the percentage of desorbed tetracycline in the simulated intestinal solution is more than the amount of desorbed tetracycline in the simulated gastric solution for all samples. Antibacterial activity of desorbed tetracycline was examined on two Escherichia coli and Staphylococcus aureus bacteria using antibacterial disc diffusion method. desorbed tetracycline in the simulated gastric solution has lost its antibacterial property against the two pathogens while desorbed tetracycline in the simulated intestinal solution has the good antibacterial function. Degradation of desorbed tetracycline in simulated gastric solution was due to the complexation of tetracycline with Al and Fe cations which were released in the desorption media by the acidic washing of montmorillonite. Also, the influence of the use of montmorillonite as a drug carrier on the tetracycline photostability, which exposed to radiation of halogen lamp at periods of 60, 120, and 180 minutes evaluated. The results of photostability experiments showed montmorillonite could protect the tetracycline against light degradation and prevents its degradation by the photon.