In this thesis an automatic control system was designed which is able to stabilize the intensity of a laser beam. This control system is employed at the test facility for the source of polarized electrons at the superconducting linear accelerator S-DALINAC in Darmstadt. The goal is to develop a regulation which is able to maintain the intensity of the output electron beam during experiments to an accuracy of 10⁻³. The control system developed within this thesis and tested with respect to miscellaneous conditions can be used as a basis for such a system. An electric circuit board was developed to implement the automatic control system which stabilizes the intensity of the laser beam in combination with an electro-optic modulator. The board was tested to check the long- and short-time stability. The time constants of the control loop have been determined as well.