Background: Selenium (Se) is an essential trace element to higher plants, animals and humans, but low Se levels are a global public health concern. Seed priming has become a basic strategy for the production of Se-riched agricultural products, but its application is still not clear in the production of Se-enrich alfalfa, hence this study was conducted for the production of Se-enriched alfalfa by seed priming with different concentrations and time on seed vigour. Methods: Seeds were primed with 0, 0.5, 1.0, 2.0, 4.0 and 8.0 mmol L-1 of sodium selenite solution for 0, 3, 6, 9 and 12 h at 20°C and their germination percentage, germination index, seedling vigour index and mean germination time were analyzed. Result: Seed vigour of alfalfa was improved by priming with low selenium (Se) concentration (0.5 and 1.0 mmol L-1), but was inhibited by high Se concentration ( greater than 2.0 mmol L-1). Hence, it must be necessary to carefully select appropriate concentration and time for the application of Se priming in alfalfa seeds. The optimal manner of Se priming in alfalfa seeds might be at 1.0 mmol L-1 concentration for 9 h.