Generally, knowledge of the radiation budget at the earth surface is very important in the investigation of the surface energetics. Net all wave radiation provides the energy that is responsible for turbulent sensible- and latent-heat exchange processes between the earth's surface and the lower troposphere, i.e. within the planetary boundary layer, as well as determining soil heat flux. Surface radiation and other data were collected in the interval of 20 minutes, at the experimental site located in the semi arid region of the institute-basin of Federal University of Campina Grande, in the city of São João do Cariri-PB northeast of Brazil from 28-02-2001 to 09-03-2001 and 07-11-2001 to 16-11-2001, the rainy and dry periods respectively. In this study the inverse theory is applied for the estimation of parameters (albedo and emissivity correction function) to study the radiation balance at the surface of the earth. A FORTRAN language code is developed for the calculation of the net radiation and the method of Levenberg-Marquardt (Press et al., 1992) is used for solving for the problem of identification. It is observed that there are significant differences between the calculated and measured daily mean values of net radiation for both dry and rainy seasons. For this a sensitivity analysis and the estimation of parameters are used applying the minimization method of Levenberg-Marquardt (Press et al., 1992). Also measurements errors of the data acquisition system are considered according to the standard deviation furnished by manufacturer. Then it is found that the values of the net radiation measured and the calculated using the estimated values of parameters (albedo and emissivity correction function) by means of inverse problem for each period are quite close to each other. The result obtained here may also be applied for the computation of prognostic surface temperature by solving the surface energy balance equation using the limited area circulation model (LAM).