Under the IEEE 802.11a/b/g WLAN specifications, this paper presents a dual-band RF FEM (front-end module) on LTCC substrate comprising two diplexers, two band-pass filters and two low-pass filters as a 802.11a/b/g SiP (system-in-package) solution. To implement, a 5GHz LNA, dual-band DPDT (double pole, double throw) switch and power detector mounted on the surface of LTCC RF module are also integrated into the proposed module where has only 5.4mm × 4.0mm × 0.9mm in size. On the side of transmitter, the insertion losses of the simulated dual-band FEM are 0.7 and 0.6dB in 2.4-2.5 and 4.9-5.9GHz frequency bands, respectively. The maximum rejection characteristic is -30dB in the second and third harmonic bands. On the side of receiver, the insertion losses are 1.7 and 1.2dB in 2.4-2.5 and 4.9-5.9GHz bands, respectively. The maximum of both the isolation and rejection characteristics is -30dB.