The present invention discloses a method, device, and system for prompting whether a portable locator has arrived on time, one of which comprising: a server, according to position point information transmitted by the portable locator, judges that there is not a position point indicative of arrival at a destination reminder area in a current preset time period and the current time has already exceeded an estimated arrival time, and then generates and issues a non-arrival reminder. By employing the present invention, the guardian confirms at any time that the monitored person carrying the portable locator does not arrive at the destination reminder area within the preset arrival time, and thereby masters the safety information of the monitored person, whereby the user experience is improved and subsequent person search effectiveness is enhanced.