A 2D object recognition algorithm based on geometry invariant and BP Network. is proposed. It can be applied to object recognition under rotation scaling translation (RST) and projection transform. By normalizing the number of pixel in the edge of image of the object to be recognized and computing the 5-point invariant in exhausting way the problem of selecting correspond points between the training and the testing object is solved, The influence to the correct recognition of the object is removed by using 5-point invariant from different view and rotation of the object image as the training set of the BP network. These makes the algorithm can be used for the recognition of the object with curve edge.