A method for predicting constellations includes the steps of: providing probability data of correlations between constellations and combined fingerprint types and blood types, and constellation fortune-telling data; detecting and classifying a fingerprint image; inputting a personal blood type; calculating probabilities of correlations between the constellations and the combined fingerprint types and blood types; and correspondingly outputting the constellation fortune-telling data according to the calculated probability. A constellation-predicting system of a preferred embodiment includes a fingerprint-image-detecting device, a blood-type-inputting unit, a calculating unit, a memory unit and a terminal unit which are connected to form the system.