The utility model belongs to the technology field of reservoir reformation of oil and gas fields, and particularly provides a key opening sliding sleeve switch device applied in multilayer separate-layer fracturing and acidifying construction of a horizontal well, the key opening sliding sleeve switch device is characterized by comprising a lock in an entering-well part and a key used for opening the part, the key comprises a central rod, a ball base provided with a steel ball and disposed at the bottom end of the central rod, an elastic slip disposed at the periphery of the central rod and adjacent to the ball base, and a protruding part disposed in a radial direction along the top end of the elastic slip and closer to the top end of the central rod; the lock comprises a body and a sliding sleeve disposed at the internal side of the body, the top end of the sliding sleeve is provided with a slip groove matched with the protruding part at the top end of the elastic slip. The key opening sliding sleeve switch device in the utility model is advantaged by removing limitation of the inner through diameter of the pipe column upon the diameter of the steel ball, overcoming defect that steps of the sliding sleeve switch are limited by the inner diameter of the pipe column, and generating ''countless'' steps of the sliding sleeve switch.