The invention discloses a charge-free reliable uploading method of an arming or disarming state. The method comprises the following steps of: a, calling an arming or disarming special line number by using an alarm host computer; b, if the special line number is busy, setting an uploading failure mark and returning to the step a, otherwise detecting and computing the hang-up signaling and time of a called party; c, transmitting an incoming call number and a line channel number; d, hanging up; e, if the incoming call number is a user number and the channel number comes from an arming special line, setting an arming state; otherwise setting a disarming state, and if the incoming call number is not the user number, not processing or performing return operation; and f, judging whether ringing times or time before the called party hangs up belong to an agreed range, if so, clearing the failure mark; otherwise hanging up, setting the failure mark and returning to the step a. The arming and the disarming states can be uploaded reliably without connecting a call of a caller, so that the problems of high communication cost of a client and unsuitability for the construction of a bus networked alarm system in built communities and scattered commercial districts are completely solved.