A thermocouple was fabricated on a trench sidewall by using photoresist spray-coating and angled exposure techniques. The thermocouple fabricated on the trench sidewall is ideal for measuring accurate temperature of microfluid in the channel. The trench structures and thermocouples were fabricated in a Si substrate. Without microfluid in the channel, thermocouples fabricated on trench sidewall and top-surface the Si substrate showed the same temperature. However, under the air-flow condition, the thermocouples on the sidewall showed lower temperature, which indicated that local temperature measurement is needed to precisely maintain the solution conditions in the microfluidics experiment.