Silicon-based channel waveguides are poled by thermal poling. A fiber-based (single mode) Mach- Zehnder interferometer is utilized to measure the linear electro-optic effect. Poling conditions (poling temperature, poling time, poling voltage) are optimized in air environment. The results show that, the electro-optic coefficient is rTM=0.059±0.001 pm/V, rTE=0.053±0.001 pm/V at the optimized conditions (-2.4 kV, 406℃, 20 min). At the same time, the waveguide has a lower threshold of poling voltage and poling temperature. An effective electro-optic signal can be observed when poling voltage drops to about 100 V or poling temperature drops to about 80℃. The results also suggest that the electro-optic coefficient increases of 15% at negative poling than positive poling.