Abstract: In this paper, the sodium atom coma of comet Bennett (1970II) is analysed. Using the Na-Dmonochromatic isophotes given by Rahe, average scale-lengths of sodium atom and its parent molecule are found by Haser's theoretic model. Converting to heliocentric distance 1 AU, they are 4.49×10⁵ km and 1.47×10⁴ km respectively. Taking typical outflow velocity, mean lifetimes of sodium atom and its parent molecule are estimated as 1.5×10⁵ seconds and 2.45×10⁴ seconds respectively. With the use of theoretic formula of Dolginov as well as other related formula and data, it is calculated that the thermal velocity and temperature of sodium atom are respectively as 2.04-5.69 km/s and 5.76×10³-4.48×10⁴ K, and hydrodynamical (outflow) velocity of sodium atom is 2.66X10 km/s when converting to heliocentric distance 1AU. Finaly, brief discussions on relevant problems are also made.