The invention provides an LED microdisplay pixel unit structure with heterogeneous monolithic integration of TFT and GaN-based LED. The structures comprises the two parts of a GaN-based LED structure and a TFT structure, wherein a u-GaN buffer layer, an n-GaN layer, an InGaN/GaN quantum well active layer, a p-GaN layer and an InGaN-based contact layer conduct epitaxy growth on a sapphire substrate of the GaN-based LED in sequence; the TFT structure conducts growth on an already produced LED chip modular construction and conducts growth of insulating layer, a TFT source electrode (also a P electrode of the LED), a TFT drain electrode, a semiconductor layer used as a TFT active layer, a gate insulation layer and a gate in sequence. According to the LED microdisplay pixel unit structure with the heterogeneous monolithic integration of the TFT and GaN-based LED, LED and TFT are integrated into one substrate, thus heterogeneous monolithic integration is achieved so that LED gray scale can be directly modulated, and electrical stability and integration level of the LED microdisplay is improved.