1. A method for indoor positioning a target device in an indoor environment, wherein a plurality of wireless ranging devices are deployed in the indoor environment, the method comprising: defining a default positioning weight with an electronic device; scanning the wireless ranging devices for obtaining a plurality of neighboring ranging devices near the target device with the electronic device; calculating a current positioning weight of each of the neighboring ranging devices with the electronic device; comparing, with the electronic device, the default positioning weight respectively with the current positioning weight of each of the neighboring ranging devices so as to obtain a plurality of reference ranging devices by selecting a portion of the neighboring ranging devices as the reference ranging devices, wherein the difference between each of the current positioning weights respectively corresponding to the selected neighboring ranging devices and the default positioning weight is smaller than a predetermined value; calculating at least one candidate coordinate with the electronic device according to a deploy coordinate of each of the reference ranging devices in the indoor environment by randomly selecting three of the reference ranging devices as selected devices while an amount of the reference ranging devices is larger than or equal to three, generating at least one of the at least one candidate coordinate according to the deploy coordinates respectively corresponding to the selected devices, and repeating the step of randomly selecting three of the reference ranging devices and the step of generating the candidate coordinate until all combinations of the three selected devices random selected from the reference ranging devices are used for generating the candidate coordinates; and estimating a positioning coordinate at which the target device is located according to the at least one candidate coordinate with the electronic device.