The invention discloses a method and device for constructing a two-way constraint initial model. The method comprises the following steps: establishing well logging elastic parameter trend informationaccording to well logging elastic parameter information; carrying out band-pass filtering on well logging elastic parameter information to obtain band-pass elastic parameter information; determiningfitting elastic parameter information according to the band-pass elastic parameter information, wherein the fitting elastic parameter information reflects the relation between spatial constraint seismic attribute and the band-pass elastic parameter, and the spatial constraint seismic attribute comprises an earthquake attribute, the correlation coefficient of which with the band-pass elastic parameter is not smaller than a preset correlation coefficient; and constructing the two-way constraint initial model according to the well logging elastic parameter trend information, the fitting elastic parameter information and first well logging low-frequency elastic parameter trend information. According to the method and the device in the invention, the well logging elastic parameter trend information comprises low-frequency information, the correlation between the spatial constraint seismic attribute and the band-pass elastic parameter is high, the model is constructed by using the low-frequency information and the spatial constraint seismic attribute, and the prediction precision of the two-way constraint initial model can be improved.