The invention discloses a portable combined auxiliary watching mobile phone holder comprising a backboard, a support board and a magnifying lens, wherein a bearing sleeve is welded with the lower endof the back board, a damping rotation shaft is rotationally connected into the bearing sleeve, a rotational placement board is connected with the side of the damping rotation shaft, a sliding groove is embedded into the rotational placement board, the front of the back board is positioned above the bearing sleeve and welded with the support plate, a placement groove is horizontally embedded into the upper surface of the support plate, a sliding strip is fit into the sliding groove in a sliding manner, a frame is welded with the upper end of the sliding strip, the amplifying lens is movably embedded into the frame, sliding penetration grooves are symmetrically arranged on two sides of the front of the back board, a pressing plate is connected between the sliding penetration grooves on two sides, a penetrating hole is formed in the middle part of the front of the back board, and a ventilator is connected into the penetrating hole via a rack. According to the portable combined auxiliary watching mobile phone holder provided by the invention, the mobile phone can be stably clamped, the mobile phone can be effectively cooled when being used for playing a game or watching a video, and the screen can be amplified via the amplifying lens connected in the sliding manner, so that the portable combined auxiliary watching mobile phone holder is convenient and practical to use, and also convenient to carry after being disassembled.