The invention discloses an installation and position-fixing device for multi-layer reinforcement bars of a three-dimensional variable-curved-surface inclined pylon and a construction method thereof. The installation and position-fixing device for the multi-layer reinforcement bars of the three-dimensional variable-curved-surface inclined pylon comprises stiff skeletons inclinedly installed in the inclined pylon and a plurality of reinforcement bar position-fixing plates arranged in the height direction of the stiff skeletons, wherein the stiff skeletons are vertically arranged around the structure of the inclined pylon; the reinforcement bar position-fixing plates are fixed to the outer sides of the stiff skeletons in the circumferential direction; the reinforcement bar position-fixing plates are formed by welding sections; and the reinforcement bar position-fixing plates are provided with a plurality of reinforcement bar position-fixing holes and concrete vibrating holes. The construction method of the installation and position-fixing device comprise installing the reinforcing bar position-fixing plates around the stiff skeletons, setting the amount of the reinforcing bar position-fixing plates based on the number of times of concrete pouring and segments of the reinforcement bars, arranging two reinforcing bar position-fixing plates respectively on and under a first segment of the reinforcing bars when installing the first segment of the reinforcement bars, and ensuring that a corresponding reinforcing bar position-fixing plate is arranged at the top of each reinforcing bar when the reinforcing bars are constructed to be higher subsequently. The installation and position-fixing device for the multi-layer reinforcement bars of the three-dimensional variable-curved-surface inclined pylon and the construction method thereof have the advantages of fixing and installing the reinforcement bars quickly and accurately, shortening the construction time and reducing the cost and construction risk.