The invention discloses a water-soil conservation method for engineering construction of an electric power transmission line. The method comprises step 1: evaluating the environment along the way of the power transmission line; step 2: building pole tower foundations, and selecting to excavate any one of a backfill foundation, an excavating foundation, a rock foundation, a pile foundation, a spiral anchor foundation, a sunk well foundation and a composite foundation; and step 3: performing the water and soil conservation on side slopes of the tower foundations: the engineer measure: in order to ensure the safety of the upper side slopes, arranging a drainage ditch in the side slopes in view of the water collecting condition above the tower position and the steep and gentle conditions of amountain, and adopting crushed rock revetments or retaining walls on the upper side slopes with a poorer water quality to protect the side slopes; and the plant measure: adopting an avoiding manner for the large trees in the construction process, and planting local grass on the constructed ground. For the water and soil conservation of the side slopes where the tower foundations are built, the action of conversing the soil can be achieved by constructing the retaining walls, and the drainage ditch is arranged in the side slopes in a manner of forming included angles with the inclined directions of the side slopes, such that the water and soil conservation effect is more excellent.