In this report, we investigate the fabrication process of 12-fold quasi-photonic crystal microcavity with size-controlled nano-post beneath for electrically-driven structure by fine-tuning the wet-etching time. By finite-element method, we simulate and analyze the heat transfer behaviors of microcavities with different nano-post sizes and shapes. From the real devices, we obtain whispering-gallery (WG) single-mode lasing action with high measured quality factor of 8 250 and low threshold of 0.6 mW when the nano-post size is as large as 830 nm in diameter. By varying the substrate temperature, WG single-mode lasing action is still obtained when the substrate temperature is as high as 70°C. Besides, the lasing wavelength red-shift rate is also improved compared with the microcavity without nano-post beneath. By varying the pump condition, lasing action is still observed at room temperature when the pump duty cycle increases to 16.0%. Thus, for electrically-driven photonic crystal microcavity lasers, this nano-post can serve as current injection pathway and heat sink at the same time.