Abstract: The China Accelerator Driven Sub-critical System, C-ADS, will use a linear accelerator delivering continuous-wave protons with an average current of 10 mA and a beam power of 15 MW to the sub-critical reactor. The main linac is an important part of the driver linac which is required to accelerate the beam from 10 MeV to 1.5 GeV. All the cavities in this part are superconducting structures. To avoid the frequently repeated beam interruptions causing damage to the reactor, the driver linac is requested to have a very limited number of beam interruptions during operation, thus fault tolerance strategy is implemented to the maximum possible extent and every possible solution is tried to ensure the highly required reliability and stability. In this paper, the baseline design of the main linac is introduced. The total length of the main linac is 306.4 m. The normalized root-mean-square emittance growth is controlled below 5%. The details of the design strategy together with the multiparticle simulation results are presented.