In order to solve the long-standing problem of high water absorption of foam concrete, the effects of triethanolamine (TEA) and zinc stearate (ZS) on the pore characteristic, mechanical property and waterproof performance of foam concrete were studied. And the modification mechanism of TEA and ZS on foam concrete was studied by contact angle test, scanning electron microscopy with energy spectroscopy and X-ray diffractometer test methods. The results show that the addition of 1.6% (mass fraction) TEA and 0.4% (mass fraction) ZS can increase the proportion of pores with a diameter of less than 500 μm, and increase 28 d compressive strength of foam concrete to 1.66 MPa. The addition of 0.4% (mass fraction) TEA and 1.6% (mass fraction) ZS can reduce the water absorption of foam concrete to 2.8%, 7.9% and 10.5% at 1, 2, 3 d, and the contact angle reaches up to 134.9°, so that the foam concrete has a hydrophobic surface. The co-doping of TEA and ZS can enhance the stability of foam in the solidified cement slurry, refine the pore structure, reduce the number of connecting pores and improve the mechanical property and waterproof performance of foam concrete.