A securing method for securing a crane on the occurrence of an exceptional event among a plurality of predefined exceptional events, the crane comprising a control-command system connected to actuators (40, 41, 42) of the crane to manage movements of the crane and of a load suspended from the crane and integrated within a processing unit of the crane, the processing unit being connected to movement, load and safety sensors placed on elements (10, 11) of the crane and delivering respective event information representative of the exceptional events, and the securing method comprises the following steps of: - establishing a list of exceptional events detectable by means of the movement, load and safety sensors and its storage in a memory unit connected to the processing unit; - associating, to each exceptional event of the list of exceptional events, with several levels of severity, each level of severity being a function of a value of the event information of at least one of the movement, load and safety sensors; characterized by - associating, to each exceptional event and to each level of severity, with a safety instruction relating to the actuators (40, 41, 42) and defining at least one degree of limitation of at least one movement of the crane; - the crane operating in a nominal operating mode, detection by the control-command system of an exceptional event from the list of exceptional events according to the event information from at least one of the movement, load and safety sensors; - evaluating by the control-command system of the level of severity of the exceptional event based on the value of the corresponding event information; - switching to secure operation, which consists in that the control-command system switches the crane from the nominal operating mode to a secure operating mode in which the control-command system applies the safety instruction associated with the severity level assessed for the detected exceptional event; - emitting by the control-command system of an alert message informing of the occurrence of the exceptional event. - establishing a list of exceptional events detectable by means of the movement, load and safety sensors and its storage in a memory unit connected to the processing unit; - associating, to each exceptional event of the list of exceptional events, with several levels of severity, each level of severity being a function of a value of the event information of at least one of the movement, load and safety sensors; characterized by - associating, to each exceptional event and to each level of severity, with a safety instruction relating to the actuators (40, 41, 42) and defining at least one degree of limitation of at least one movement of the crane; - the crane operating in a nominal operating mode, detection by the control-command system of an exceptional event from the list of exceptional events according to the event information from at least one of the movement, load and safety sensors; - evaluating by the control-command system of the level of severity of the exceptional event based on the value of the corresponding event information; - switching to secure operation, which consists in that the control-command system switches the crane from the nominal operating mode to a secure operating mode in which the control-command system applies the safety instruction associated with the severity level assessed for the detected exceptional event; - emitting by the control-command system of an alert message informing of the occurrence of the exceptional event.