Abstract: Using a two box model,the dependence of ¹⁴C concentration in the atmosphere on the ¹⁴C production rate,the inventories and residence time of carbon in the atmosphere and ocean are deduced.Then a formula for calculating the increment of ¹⁴C nucleon number in atmosphere after a supernova explosion according to tree ring ¹⁴C data and a formula for estimating the gamma ray energy output emitted from the explosion are successively given.