The transmission properties of the sil icon slot optical waveguides are researched.The relationships between the slot o ptical power and the widths of the slot and silicon strip are studied by using F DTD method. Results show that silicon slot optical waveguides can offer good power confineme nt efficiency which can be as high as 30%.The optical power confinement and its optimization are analyzed.The waveguide parameters of the slots can be optimized by taking the optical power and power densit y into account,by which a best field distribution can be obtained.The field distribution at the cross section shows an excellent confinement along x direction and a Gaussian distribution along y direction. The effects of the t hin silicon bottom slab on the power confinement are studied.A 100nm thick silicon bottom slab will decrease the po wer in the slot by 50%.A slot waveguide is fabricated on SOI wafer by using electron beam lithography and plasma etching technologies.The transmission loss is studi ed experimentally.Results show that it has a good transmission loss as low as 13.5dB/cm.