A simultaneous optical visualization experimental system was set up, and a parallel triangle silicon microchannel heat sink was used as the test section. Five platinum film microheaters was etched at the top glass cover surface and located at the microchannel entrance, acting as a seed bubble generator array. The microscale flow boiling instability under different seed bubble frequencies was experimental examined. The results show that the seed bubble frequency is an important parameter to control flow boiling instability. In the single liquid flow region, seed bubbles have negligible effect on flow. In the two-phase flow region, with heat flux increasing, pressure drop increases linearly and the temperature of the heating wall surface increases exponentially. Moreover, higher pressure drop could be approached with lower wall temperatures and higher bubble triggering frequency. With the same heat flux, the seed bubbles triggered with high frequency can completely eliminate flow boiling instabilities, heating wall temperature could be dramatically decreased, and the uniformity of the temperature could be promoted significantly.