Hydraulic system for actuating the hydraulic actuators of a working machine; the hydraulic system comprises: a high-pressure oil delivery; a low-pressure oil discharge; at least one first slide valve which comprises a first spool, which is axially slidable, and controls a first hydraulic actuator; a first control which can be directly actuated by an operator by means of a control lever and controls the position of the first spool of the first slide valve; and a first pressure compensator which is hydraulically connected to the first slide valve, has a main inlet, which can be connected to the delivery by means of the first slide valve, and a main outlet, which can be connected to the first hydraulic actuator by means of the first slide valve, and presents a frontal chamber which determines the control of the pressure compensator and is permanently connected to the main inlet; the hydraulic system being characterised in that it comprises: a first drainage line, which connects the frontal chamber of the first pressure compensator to the discharge and is provided with a drainage valve which is actuated in order to open or close the first drainage line; a signal line which is connected to a rear chamber of the first pressure compensator; wherein the signal line has a node; a second drainage line which connects the node of the signal line to the discharge; wherein the second drainage line is connected directly to the signal line in correspondence of said node; and, a second safety slide valve comprising a second spool which is fixed to the first spool of the first slide valve, is axially sliding and is arranged along the second drainage line in order to close or open the second drainage line itself. a high-pressure oil delivery; a low-pressure oil discharge; at least one first slide valve which comprises a first spool, which is axially slidable, and controls a first hydraulic actuator; a first control which can be directly actuated by an operator by means of a control lever and controls the position of the first spool of the first slide valve; and a first pressure compensator which is hydraulically connected to the first slide valve, has a main inlet, which can be connected to the delivery by means of the first slide valve, and a main outlet, which can be connected to the first hydraulic actuator by means of the first slide valve, and presents a frontal chamber which determines the control of the pressure compensator and is permanently connected to the main inlet; the hydraulic system being characterised in that it comprises: a first drainage line, which connects the frontal chamber of the first pressure compensator to the discharge and is provided with a drainage valve which is actuated in order to open or close the first drainage line; a signal line which is connected to a rear chamber of the first pressure compensator; wherein the signal line has a node; a second drainage line which connects the node of the signal line to the discharge; wherein the second drainage line is connected directly to the signal line in correspondence of said node; and, a second safety slide valve comprising a second spool which is fixed to the first spool of the first slide valve, is axially sliding and is arranged along the second drainage line in order to close or open the second drainage line itself. a first drainage line, which connects the frontal chamber of the first pressure compensator to the discharge and is provided with a drainage valve which is actuated in order to open or close the first drainage line; a signal line which is connected to a rear chamber of the first pressure compensator; wherein the signal line has a node; a second drainage line which connects the node of the signal line to the discharge; wherein the second drainage line is connected directly to the signal line in correspondence of said node; and, a second safety slide valve comprising a second spool which is fixed to the first spool of the first slide valve, is axially sliding and is arranged along the second drainage line in order to close or open the second drainage line itself.