The temporal and spatial distributions of the plasma temperature during the dissipation process of lightning are calculated theoretically by applying the equation of motion，the equation of continuity and the equation of energy conservation of hydrostatics. The result shows that the temperature decay at a given radius is quicker in the earlier stage and slower in the later stage; Furthermore，the higher the original temperature，the quicker the decay. The temperature decays slower when the radius becomes larger. At the same time，the larger the radius of lightning channel，the greater the temperature gradient, and vice versa. According to the time and position of freezing temperature of NO，we can conclude primarily that NOx are produced in the channel of less than 9 mm radius in the time within 50 ms after the lightning return stroke.