The present invention discloses an S/L-frequency band planar self-tracking antenna. The S/L-frequency band planar self-tracking antenna comprises a radome, an antenna housing, an inner cavity supporting structure, an antenna array plane printed circuit board, an S-frequency band network printed circuit board, an S-frequency band antenna unit, an L-frequency band antenna unit, an S-frequency band network printed line, an L-frequency band network printed line, an S-frequency band sum-difference modulator and an S-frequency band low-noise filtering assembly; the S-frequency band antenna unit includes an S-frequency band orienting sheet, an S-frequency band radiation patch, an S unit supporting column and a feed pin; the L-frequency band antenna unit comprises an L-frequency band orienting sheet, an L-frequency radiation patch and an L unit supporting column; the S-frequency band network printed line is arranged at the lower surface of the S-frequency band network printed circuit board; the L-frequency band network printed line is arranged at the upper surface of the antenna array plane printed circuit board; and the S-frequency band sum-difference modulator and the S-frequency band low-noise filtering assembly are installed at the lower surface of the inner cavity supporting structure. The S/L-frequency band planar self-tracking antenna of the invention has the advantages of decreased size, reduced weight and improved gain.