The invention discloses a self-adaptive adjustment device of a photovoltaic support system. The self-adaptive adjustment device comprises a support base and an adjustment mechanism; the adjustment mechanism comprises two first adjusting plates, two second adjusting plates and a rotating shaft; the rotating shaft is used for pivoting the two second adjusting plates at the two sides of the support base respectively; the two second adjusting plates are located between the two first adjusting plates; a waist hole is formed in each first adjusting plate; the rotating shaft is connected with the waist holes in a penetrated manner; an abutting part is arranged at one end of the rotating shaft while the other end of the rotating shaft is in screw connection with a nut; the end face, close to each second adjusting plate, of each first adjusting plate is provided with an up-pressing oblique plane; each second adjusting plate is provided with a pressed oblique plane; the up-pressing oblique plane inclines from the upside to the downside in a direction of being gradually far away from the second adjusting plates; a compressing part is arranged at the top part of each first adjusting plate; the compressing parts are located above the top parts of the second adjusting plates; and the two compressing parts and the top end faces of the two second adjusting plates form a clamping gap. The self-adaptive adjustment device of the photovoltaic support system realizes self-adaptive clamping and adjustment for a keel, and can realize connection without punching the keel.