The invention discloses an improved H-infinity control method for a grid-connected inverter applicable to a weak power grid. The method comprises the steps of S1, building a traditional H-infinity control model of the grid-connected inverter according to electric parameters and control parameters in the grid-connected inverter; S2, processing the control model in the step S1 by adopting an indirect control law to eliminate items which are influenced by the grid impedance in traditional H-infinity to lead to changes in parameter and structure of a controller; and S3, solving the controller gain of the improved H-infinity control by using an H-infinity theory. The improved H-infinity control method has the beneficial effects that influences imposed on output current of the grid-connected inverted by the grid impedance is eliminated, the grid-connected inverter system is enabled to be stable under the weak power grid, a given value of the output current can be accurately tracked, and the output current has good current quality.