Flood disasters cause both direct and indirect economic losses to industrial systems, and indirect economic losses may be much higher than direct economic losses. Studying indirect economic losses is of great significance for disaster risk reduction. Based on the input-output model, this study used the direct economic loss data of flood disasters in Hubei Province in 2016 to evaluate indirect economic losses under different flood water depth, from the perspective of sectorial interconnectedness. The results show that: 1) With the increase of flood water depth, direct economic losses and indirect economic losses increase accordingly. 2) For most industrial sectors, indirect economic losses caused by industrial interconnectedness are higher than direct economic losses. However, when flood water depth is shallow, some industrial sectors with more intensive fixed assets are more affected by flood disasters, resulting in higher direct economic losses. 3) The total indirect economic losses show a nonlinear relationship with the total direct economic losses, but with the same trend. When the flood water depth is greater than 2.093 m, indirect economic losses are about 1.15 times of direct economic losses.