The invention discloses a semitrailer launching vehicle for launching a target projectile, which comprises leveling supporting legs (3), a rotary table (5), a bracket (6), a support (9), a guide rail (7), a servo device (4), a control device (8) and a semitrailer chassis (2). The leveling supporting legs (3), the rotary table (5) and the support (9) are fixedly connected with the semitrailer chassis (2); the leveling supporting legs (3) are used for leveling the semitrailer chassis (2); the control device (8) controls the rotary table (5) to rotate to an initial azimuth angle; the servo device (4) drives the bracket (6) to be erected to a set angle; the guide rail (7) is used for keeping an initial direction of the target projectile; the support (9) is used for supporting the bracket (6). The semitrailer launching vehicle is drawn by a tractor; different target projectiles are replaced by modifying the size of the guide rail; besides the semitrailer chassis (2), the components of the semitrailer launching vehicle have no interface relation with the tractor, so that workload of transformation is reduced; the semitrailer launching vehicle is high in adaptability and low in cost.