For the first time, a novel Si-waveguide-integrated InGaAs/InAlAs avalanche photodiode (APD) on the SOI platform was realized, in which light propagating along the Si waveguide is evanescently absorbed by an overlaying InGaAs layer bonded on it. The integrated-APD exhibits a high responsivity of 0.99 A/W at 1570 nm, a dark current (Idark) of 7.6 nA at 90% breakdown voltage (Vbr), and a maximum gain of larger than 70. The good quality of the bonded III-V epi-layers and promising performance of the fabricated waveguide-integrated APDs has been realized where the negligible variation induced by the bonding process has been confirmed.