The invention discloses a simultaneous positive and negative ion analysis method in an ion trap. The method is characterized in that the annular ion trap is enclosed by two independent ion trap tracks, and an ion analysis area of each ion trap track is enclosed by four independent plate electrodes. The method comprises that in each of an ion input and separation phase and an ion analysis phase ofthe annular ion trap, DC constant voltages in opposite directions are acted on the two ion trap tracks respectively, ions are separated into the two ion trap tracks according to positive and negativestates when input to the annular ion trap, so that in the ion analysis phase, one ion trap track carries out positive ion analysis while the other ion trap track carries out negative ion analysis. Thus, positive ions and negative ions are separated from each other and analyzed simultaneously in the same ion trap.