The utility model discloses a waterproof foundation ditch, waterproof foundation ditch includes along underground continuous wall (1) and the foundation ditch back cover structure of basad construction of the profile construction of foundation ditch (2), foundation ditch back cover structure with underground continuous wall (1) joint to the inside that makes the foundation ditch keeps apart with outside the elder generation of underground continuous wall (1) is under construction groove section (12) to be under construction after and connects (3) through the I -steel between groove section (11) and form the seam, the I -steel connects the orientation of (3) after be under construction groove section (11) one side edge of a wing length to be greater than the orientation be under construction the earlier edge of a wing length of groove section (12) one side. The inside of foundation ditch keeps apart with outside, and the I -steel connects to be under construction after with and forms crooked seepage paths between the section of groove, can increase the degree of difficulty of the inside and outside lateral seepage of foundation ditch, and form the waterproof system of fully enclosed, can effectually prevent the inside and outside groundwater intercommunication of foundation ditch, has effectively avoided falling the adverse effect to the foundation ditch surrounding environment that the drainage caused owing to be under construction.