The invention provides a resistance adjusting method of a combined microcomputer rheostat. The method comprises the following steps: 1, determining the control target values of a large rheostat controller, a medium rheostat controller and a fine rheostat controller; and 2, respectively sending the target resistances obtained in step 1 to the large rheostat controller, the medium rheostat controller and the fine rheostat controller as the control target values of the above three controllers, and adjusting the resistances of the large rheostat controller, the medium rheostat controller and the fine rheostat controller;. Rheostat depended by the method is a wide range rheostat formed by combining three rheostats with connected measuring ranges, so the rheostat has large range and very high resolution; and the resistance of a slide rheostat is set on a microcomputer, and the obtained target resistance is transmitted to all the rheostats to realize automatic adjustment and control, so the adjusting efficiency of the rheostats is effectively improved, and the adjusting danger of the rheostats is reduced.