The thesis deals with the problem of estimating lightning current parameters, which can be described using a double-exponential approximation or the Heidler function. The unknown parameters of the lightning current approximation function are estimated using the Marquardt method, which was developed by upgrading the Gauss-Newton method. The second chapter describes the characteristics and approximations of lightning current. The two most commonly used lightning current approximations are: the double-exponential function and the Heidler function. In the third chapter, an algorithm for estimating lightning current parameters described using the double-exponential function is developed and selected examples are solved. In the fourth chapter, an algorithm for estimating lightning current parameters described using the Heidler function is developed and selected examples are also solved. In all cases of estimating the parameters of the approximation function, two requirements must be met: the duration of the lightning current front and the half-life of the lightning current crest. In addition, possible additional requirements are: the total lightning current charge and/or the specific energy of the lightning current. In the process of estimating lightning current parameters, it is not possible to fully satisfy all the set conditions, which are satisfied by the Marquardt method. However, in all solved examples, deviations from the set conditions are negligible. In addition, the developed algorithms for estimating lightning current parameters are reliable because convergence is ensured in all cases, regardless of the given initial conditions.