A negative pressure ink supply system includes (1) a primary ink cartridges, (2) a secondary ink cartridges, which are connected by means of an ink tubes with the negative pressure ink cartridge assemblies provided between the secondary ink cartridges and the jet head. The ink, pumped from the primary ink cartridge, is put into the secondary ink cartridge, wherein it is supplied to the negative pressure ink cartridge and then in turn from the negative pressure ink cartridge to the jet head. The liquid level in the secondary cartridge is lower than the jet head surface and adjustable. The negative pressure ink supply system is suitable for image-printing equipment by supplying liquid ink, such as large format machines, portrait machines, plotters, etc.