Enzymaticactivity and biochemical responsesof two citrus rootstocks [sour orange (Citrus aurantium L.) and trifoliate orange (Poncirus trifoliata Raf.)] to in vitro salinitystress were studied. Explants of both rootstocks were transferred to Murashige and Skoog (MS) solid proliferation medium containing 8.9 µM Benzyladenine (BA) and 0.5 µM Naphthaline Acetic Acid (NAA) supplemented with 0, 50, 100, 150, 200 mM of sodium chloride (NaCl) with six replicates. After six weeks, results showed that, rootstock, salinity levels and their interaction, had a significant effect on all of the measured parameters. Antioxidant enzymes activity such as: catalase, peroxidase, ascorbate peroxidase, proline content, soluble sugars and malondialdehyde (MDA) content increased in both rootstocks by increasing salinity level. The amounts of increasing in sour orange rootstock were greater than trifoliate orange, except for peroxidase enzyme and MDA. Total protein content decreased by increasing salinity level in both rootstocks. Sour orange rootstock has higher total protein content than trifoliate orange. According to the results, sour orange rootstock was more tolerant to salt stress.