A modulation recognition method and device for digitally modulated signals with multi-level magnitudes are provided. The modulation recognition method includes selecting plural of quantization sizes used to construct plural of statistic histograms related to the magnitude of a sequence of data, setting up an off-line processing to extract plural of useful feature patterns for each modulation type of interest, receiving a sequence of samples of the modulated object signal and constructing plural of statistic histograms related to the magnitude of these samples, and adopting a hierarchical classification method for modulation recognition. It can be applied to the adaptive-modulation communication system, software defined radio, digital broadcasting systems and military communication systems. It can also be integrated with modulation recognition techniques for other types of modulated signals to function in a universal demodulator. It recognizes digitally modulated signals of multi-level magnitudes with low computational complexity in advancing the efficiency of communication systems.