Purpose: Traditionally, the reconstruction of fluorescence diffuse optical tomography (FDOT) images requires anatomical images as prior information. To integrate anatomical information about tumors or soft tissues into FDOT, additional equipment and procedures are required, involving co-registration, contrast-agent injection, and alignment. Methods: Herein, we propose the adaptive spatial prior approach for reconstructing FDOT images, implemented by using an initial guess of the tumor size and location for single and multi-tumor cases. This technique is most appropriately used when FDOT is combined with limited structural information or a different structural imaging system. This method iteratively modifies the location starting from the estimated location. Results: We conduct simulations, phantom experiments and experiments on meat tissue using the adaptive spatial prior method. Conclusions: The results of these studies demonstrate the feasibility of the adaptive spatial prior approach for FDOT imaging.