The embodiment of the invention provides a modulation method and device based on dual-path multi-directional probability mapping. The method comprises the following steps: performing serial-to-parallel conversion on a to-be-modulated signal to generate six sub-signals, performing probability mapping on four sub-signals to obtain a mapping signal set; determining an amplitude mapping result corresponding to a signal value of first two mapping signals in the mapping signal set at each moment according to a first constellation diagram, and determining a location mapping result corresponding to the signal value of last two mapping signals in the mapping signal set and two sub-signals in the six sub-signals except four sub-signals at each moment according to the second constellation diagram, and acquiring an APPM signal according to the amplitude mapping result and the location mapping result. Through the modulation method provided by the embodiment of the invention, the to-be-modulated signal is mapped as the mapping signals with different probabilities, and then the APPM signal is acquired according to the first constellation diagram and the second constellation diagram, a complicatedconstellation diagram is unnecessary to design, and the complexity of the signal modulation can be lowered.