This paper proposes a two-dimensional heterostructure photonic crystal on a GaN-based active platform for achieving a resonant microcavity in the blue band with a high quality （Q） factor and small mode volume （V_m）. The working mechanism of the heterostructure photonic crystal resonator is explained through band structure analysis. Based on the band edge and band gap principles applicable to photonic crystals， photonic in-plane feedback， a high Q factor resonance， and out-of-plane vertical emission are realized. The resonance characteristics of the core and cladding regions using different cavity parameters are studied by finite difference time domain （FDTD） simulation. The relationships among the microcavity structure and the resonance Q factor， cavity loss， resonance frequency， and V_m are discussed. These findings pave the way for designing high-Q/V_m resonators in the blue band and establishing a method with a theoretical basis for studying heterostructure photonic crystal microcavities with excellent resonance characteristics.