The invention relates to the field of currency counting machines, in particular to an infrared image detection system for a plastic money window, which solves the problem that the existing plastic money detection cannot quickly, accurately and effectively identify the denomination. The detection device consists of two groups of infrared emitting devices and infrared receiving devices which are fixedly arranged on a money feeding channel, wherein each infrared emitting device comprises a light guide column, an emitting seat, an emitting sensor circuit board, an emitting sensor and a fluorescentsilica gel partition block, each infrared receiving device comprises a transmission grating glass sheet, a sensor sealing gasket, a receiving sensor circuit board, a receiving sensor and a receivingseat containing a grating. An infrared image of a banknote surface can be formed by collecting the light transmission data through a matrix. The infrared image detection system for the plastic money window can reliably distinguish the currency and denomination of various plastic moneys and detect the damage thereof, thereby greatly improving the capability of identifying the plastic moneys. By extending functions, the infrared image detection system for the plastic money window can also conduct contour identification and the calculation of the area of face value.