Laser resistor trimming is achieved by positioning a very thin laser beam on a thin-film or thick-film resistor. The beam cuts the resistor according to a computer-predetermined program, thus trimming the resistance value by changing the cross-sectional area of the resistor. The resistance value is measured in real time through the high-speed measurement system while the laser is cutting the resistance, so that it is constantly approaching the target resistance value. When the resistance reaches the target resistance value, the laser beam is turned off to realize precise trimming of the resistance. The laser trimming system has a variety of trimming functions. It can trim thick or thin film resistor networks, capacitor networks, ceramic-based thin film integrated components, and realize function trimming of hybrid integrated circuits.