The embodiment of the invention discloses a method and a device for improving the efficiency of E class power amplifiers. The method includes: A. the efficiency of a power amplifier before and after regulating parallel capacitive reactance are respectively obtained; B. according to the regulated efficiency of the power amplifier before and after regulating parallel capacitive reactance, the parallel capacitive reactance is adjusted; the steps A and B are repeated until the efficiency of the power amplifier does not increase and series connection capacitive reactance and/or series connection inductance are adjusted; C. the efficiency of the power amplifier before and after regulating the series connection capacitive reactance and/or inductance are respectively adjusted; D. the series connection capacitive reactance and/or inductance are adjusted according to the efficiency gained in the step C; the steps C and D are repeated until the efficiency of the power amplifier does not improve. The embodiment of the invention adjusts the parallel capacitive reactance as well as the series connection capacitive reactance and/or inductance by monitoring the efficiency of the power amplifier before and after the adjustment until the efficiency does not improve any more, thus improving the efficiency of the E class power amplifiers.