The absorption and emission characteristics of single plasma channel produced by femtosecond laser pulse in air have been investigated theoretically. Analytical expressions of Rosseland mean absorption coefficient and radiant energy fluence rate are deduced. It is found that our analytical results are consistent with data from TOPS opacities database. The dependences of absorption and emission characteristics on initial laser parameters are studied. Calculation of such quantities for air plasma channel induced by laser pulse with 800 nm central wavelength and 40 fs pulse width is carried out. Results indicate that,in the case of single filament,the average Rosseland mean absorption coefficient is 0.0270 cm-1,and total radiant energy fluence rate reaches 7.87×1010 W/m2. Incident fs laser with shorter pulse width and longer wavelength furns out advantage to producing weak absorbing and strong radiative plasma channel.