In this work, we demonstrate a systematic platform consisting of Si(100)/GaN monolithic heterogeneous integration CMOS inverters and GaN power HEMTs for high switching frequency and high power applications. Si(100)/GaN monolithic integration material was fabricated by transfer printing and self-aligned etching technology. Then, monolithic heterogeneous integration inverters consist of normally-off Si(100) PMOSFETs and normally-off GaN NMOS-HEMTs, and normally-off GaN power HEMTs were fabricated simultaneously on the Si(100)/GaN integration platform. The Si(100)/GaN monolithic heterogeneous integration inverters exhibited excellent low-level noise margin (NM_L) of 0.47 V and high-level noise margin (NM_H) of 0.45 V at a supply voltage (V_DD) of 1 V. Moreover, a high peak voltage gain of 30.81 V/V was attained. The decent characteristics of a I_ON/I_OFF exceeding 10⁹, a threshold voltage (V_TH) of 2.7 V, and a breakdown voltage (V_BR) of 2109 V leading to a power-figures-of-merit (PFOM) of 1.45 GW cm² were achieved in the monolithic integrated normally-off GaN power HEMTs with a LGDof 19.5 μm. These excellent results demonstrate a promising potential of the Si(100)/GaN monolithic heterogeneous integration devices for high switching frequency and logic integrated circuit applications.