A host machine comprising an ink-staining anti-theft cash box mounted in a housing of the host machine for receiving each bill being delivered from a bill passage in said housing and pressed by a bill presser unit of said host machine, said ink-staining anti-theft cash box comprising a cash box, an ink-jet module and an anti-theft security device, wherein: said cash box comprises a box body detachably mounted to mounting walls of said host machine, said box body comprising an accommodation chamber, a front opening disposed in communication with said accommodation chamber and facing toward said bill presser unit and a pressure board movably mounted in said accommodation chamber for receiving each bill being pressed by said bill presser unit; said ink-jet module comprises an ink cartridge mounted in said box body, an continuous ink path from an inlet to an outlet in/through which ink is flowing, the ink path being defined in the ink cartridge in one plane with the inlet and the outlet, the ink inlet and the ink outlet being respectively located on two opposite ends of said ink path, the ink path being curved and having alternating straight elements which change direction in repeated 90° turns, an ink tube connected to said ink inlet and a nozzle assembly connected to said ink outlet and disposed in communication with said accommodation chamber; said anti-theft security device comprises a gas cylinder sealed with an air seal diaphragm and mounted in said box body, a needle valve unit, a drive unit and a trigger unit adapted for triggering said drive unit upon detection of separation of said cash box from said host machine, said needle valve unit being connected to said ink tube to create a gas passage, said drive unit of said anti-theft security device comprises a motor, a transmission mechanism drivable by said motor, a linkage lever pivotally coupled to said transmission mechanism and a slider pivotally connected to said linkage lever opposite to said transmission mechanism for carrying said gas cylinder.and said needle valve unit being movable between a first position where said drive unit is inactivated and said needle valve unit is aimed at and kept apart from said air seal diaphragm of said gas cylinder and a second position where transmission mechanism drivable by said motor is activated to move said linkage lever, said linkage lever biases said slider to carry said gas cylinder in a transverse position toward said needle valve unit and said needle valve unit pierces said air seal diaphragm of said gas cylinder for releasing a compressed gas from said gas cylinder through said ink tube into said ink cartridge to force said ink out of said nozzle assembly for staining storage bills in said box body. said cash box comprises a box body detachably mounted to mounting walls of said host machine, said box body comprising an accommodation chamber, a front opening disposed in communication with said accommodation chamber and facing toward said bill presser unit and a pressure board movably mounted in said accommodation chamber for receiving each bill being pressed by said bill presser unit; said ink-jet module comprises an ink cartridge mounted in said box body, an continuous ink path from an inlet to an outlet in/through which ink is flowing, the ink path being defined in the ink cartridge in one plane with the inlet and the outlet, the ink inlet and the ink outlet being respectively located on two opposite ends of said ink path, the ink path being curved and having alternating straight elements which change direction in repeated 90° turns, an ink tube connected to said ink inlet and a nozzle assembly connected to said ink outlet and disposed in communication with said accommodation chamber; said anti-theft security device comprises a gas cylinder sealed with an air seal diaphragm and mounted in said box body, a needle valve unit, a drive unit and a trigger unit adapted for triggering said drive unit upon detection of separation of said cash box from said host machine, said needle valve unit being connected to said ink tube to create a gas passage, said drive unit of said anti-theft security device comprises a motor, a transmission mechanism drivable by said motor, a linkage lever pivotally coupled to said transmission mechanism and a slider pivotally connected to said linkage lever opposite to said transmission mechanism for carrying said gas cylinder.and said needle valve unit being movable between a first position where said drive unit is inactivated and said needle valve unit is aimed at and kept apart from said air seal diaphragm of said gas cylinder and a second position where transmission mechanism drivable by said motor is activated to move said linkage lever, said linkage lever biases said slider to carry said gas cylinder in a transverse position toward said needle valve unit and said needle valve unit pierces said air seal diaphragm of said gas cylinder for releasing a compressed gas from said gas cylinder through said ink tube into said ink cartridge to force said ink out of said nozzle assembly for staining storage bills in said box body.