In this report, we propose a square lattice photonic crystal hetero-slab-edge microcavity design. In numerical simulations, three surface modes in this microcavity are investigated and optimized by tuning the slab-edge termination τ and gradual mirror layer. High simulated quality (Q) factor of 2.3 × 105 and small mode volume of 0.105 μm 3 are obtained from microcavity with τ = 0.80. In experiments, we obtain and identify different surface modes lasing. The surface mode in the second photonic band gap shows a very-low threshold of 140 μW and high Q factor of 5,500, which could be an avenue to low-threshold optical lasers and highly sensitive sensor applications with efficient light-matter interactions.