The invention discloses a planar spiral inductor with wide-narrow-alternatingly line width and space, which can be used for an RF integrated circuit. The planar spiral inductor adopts the structure that a spiral inductive insulation layer is arranged on a silicon substrate; the metal thin film is coated on the insulation layer to etch an inductive bottom layer metal layer, so the insulation layeris deposited on the bottom layer metal layer; through holes are formed on the insulation layer so as to connect the bottom layer metal layer and the spiral inductor layer; and the metal thin film is coated on the insulation layer to etch a spiral inductive metal layer with a multi-turn coil; and the pattern of the coil is formed through conductive metal. According to the invention, the metal coilis alternately changed in width form the outer ring to the inner ring, whereas the space is alternately changed in width form the inner ring to the outer ring, thereby reducing the Ohm wastage causedby equivalent resistors connected in series, lowering the proximity effect of the metal wires, improving the quality factor Q value of the spiral inductor, increasing the mutual induction of the wirecoils, and also improving the inductance value of the spiral inductor.