The invention provides a telescopic and clamping type mobile charging device and a fixing method based on such a device. The mobile charging device comprises a clamping mechanism and a stretching mechanism. The clamping mechanism comprises a sliding plate, a telescopic clamping plate and a sliding assembly. The telescopic clamping plate and the sliding plate cooperate with the housing of the mobile charging device in a sliding manner through the sliding assembly. One end of the housing of the mobile charging device fits the sliding plate, and the other end fits the telescopic clamping plate. The stretching mechanism comprises a connection rod, an elastic damper and a positioning rod. The fitting part between the housing of the mobile charging device and the telescopic clamping plate is provided with a stretching groove. One end of the connection rod is connected to the telescopic clamping plate. According to the invention, a user can still use a device when the device is being charged, and the use of the device being charged is not affected by a charging position. As a result, a user can use the device with increased satisfaction.