A method and an arrangement in power transmission of a forest machine (1), theforest machine comprising a primary power source (5) for generating powerrequired for moving and controlling the forest machine and/or actuators (6, 7)therein. In the present method and arrangement, at least part of the powergenerated by the primary power source (5) is converted into electric energy bymeans of a generator arrangement (8). This electric energy can be stored atleast partly in an electricity storage means (9), from which part thereof canbe used, when required, for generating pressure medium- transmitted power forimplementing a pressure medium-transmitted function of the forest machine (1)or at least one actuator (6, 7) therein.
