Image acquisition by image acquisition card combined with camera is a primary method to acquire image data in various image-processing systems, especially in applications related to dynamic video.A design of 1:1 mode image acquisition card based on PCI bus is proposed, selecting the proper sampling frequency so that the ratio of horizontal pixel interval to vertical one is 1:1. It resolved the geometric distortion of images acquired by general image acquisition card. Image data acquired by 1:1 mode image acquisition card can be widely used in real-time image processing systems to improve the performance without geometric rectification by software.