A CMOS compatible silicon microdisk modulator was fabricated.The device size is reduced by using the microdisk resonator.The overlap between mic rodisk resonance mode and electric field is increased by using interleaved PN junctions ,and hence the plasma dispersion effect is enhanced.Experimental results reveal that the resonance can be red-shifted under a reverse bias,resulting in transmission extinction ratio of ~9dB at the original resonance wavelength.The modulation speed can re ach 10Gbit/s measured using a pseudo-random bit sequence (PRBS) signal with 3V peak-to-peak value under 1.5V reverse bias.The power consumption is 44.1pJ /bit.