The relativistic mean-field (RMF) theory is used to calculate the properties of A = 7-9 drip-line nuclei ~7Li,~(7;9)Be, ~(8;9)B, and ~9C. Systematic deviations between experimental and theoretical binding energies are found. Possiblereasons of these systematic deviations are discussed in terms of pairing energy. The root-mean-square (rms) radii ofmatter distributions for these nuclei agree with the experimental data quite well. The one-proton halo structure in ~8Bis reproduced well, and the two-proton halo in ~9C is predicted. The calculations show that the RMF theory is valid instudying the properties of light drip-line nuclei. The relativistic mean-field (RMF) theory is used to calculate the properties of A = 7-9 drip-line nuclei ~ 7Li, ~ (7; 9) Be, ~ between experimental and theoretical binding energies are found. Possiblereasons of these systematic deviations are discussed in terms of pairing energy. The root-mean-square (rms) radii ofmatter distributions for these nuclei agree with the experimental data quite well. The one-proton halo The calculations show that the RMF theory is valid instudying the properties of light drip-line nuclei.