The invention discloses a method for acquiring a number of a paper currency or a financial bill. The preset position on a conveying passage is provided with a number acquisition device according to the layout position of the number. The method comprises the steps of: acquiring a regional image where the number may appear when the paper currency and the financial bill to be detected reaches the preset position; detecting the regional image, and judging whether the regional image contains the number of the paper currency; and extracting the number from the image. The invention also provides a device for acquiring the number of the paper currency or the financial bill, which comprises an image acquisition unit, a detection unit and a number extract ion unit. The invention also provides a corresponding method and a corresponding device for identifying the paper currency or the financial bill. According to the invention, only a region which may contain the number needs to be extracted, which can ensure that the processed redundant information amount is minimum, the resolution of the region to be identified is highest, the useful information amount is increased, and the identification accuracy is improved, so that the number of the paper currency or the financial bill can be quickly and accurately acquired and can be identified and managed.