A double-row anti-slide pile system can effectively control large landslide thrusts within a large-scale talus landslide. In such a system, the separation of the up-slope and down-slope rows of piles is a key factor that impacts the distribution of their internal forces. Common large-scale talus landslides, which are characterized by a curved slip surface that is gentle in the front and steep in the rear, are discussed in this paper. The mechanical characteristics of double piles positioned at a net separation between rows of 23.8a (where a is the length of the long side of rectangular cross section of a pile), 16.3a, 10.7a, 6a and 2a have been investigated by finite element analyses. Based on this investigation, internal forces of the pile body are found to not change with row separation monotonously. Rather, they are closely related to the pile positions (i.e. within the anti-slide or slide section of the slip surface). When the rear piles are fixed at the anti-slide section of the landslide mass, the landslide thrust on the up-slope side of the rear piles and the slope resistance on the down-slope side increase gradually as the row separation becomes larger. As a result, the comprehensive mechanical effect of double piles tends to worsen. We advise that the optimal net separation between rows of piles is 2a to 4a.