Aiming at the problem that the existing evaluation methods of water seepage and accumulation of bridge deck pavement waterproof interlayer are not perfect, digital image processing technique was used to quantify the pore distribution of interlayer, and the evaluation method of water seepage and accumulation was proposed based on indexes of porosity, pore number, and equivalent pore diameter. Then, a three-dimensional reconstruction model of pores in bridge waterproof interlayers was established and the structure of the pores was visually presented. At last, combining with the transverse permeation tests of 5 typical interlayers, the reliability of the digital image analysis technique in evaluating water seepage and accumulation of interlayers was verified. Test results show that synchronous surface dressing had rich pore distribution and large pore size, which is easy to permeate water and can supply sufficient space for water accumulation. The pores of AC-5 and slurry seals were dense and small, making the seepage resistance of AC-5 better than that of synchronous surface dressing. The porosity of the SBS modified emulsified asphalt as interlayer was small, and there was little connectivity between pores due to the dispersion of pores. Therefore, the waterproof performance of SBS modified emulsified asphalt used as bridge waterproof interlayer was the best.