Abstract: This invention provides a device preventing printers from jam on the jet nozzle, comprising of a cartridge filled with ink and with an ink outlet contacting the nozzle of printer. It features with: a liquid lighter than and not dissolvable in the ink in the cartridge and an absorbent at the outlet in the said cartridge. Thus, when the ink in the cartridge is used up, the absorbent will absorb the liquid, which prevents both the ink from drying to congregate into a mass and the outlet from drying. Therefore, it can keep the nozzle of printer wet and unblocked. Furthermore, it can also prevent the nozzle from blocking due to the chemical combination between different brands of ink used.