This study aims to address the problems of inaccurate predictions, incomplete losses composition, and the limitation to the single operating condition in current hydro-mechanical continuously variable transmission (HMT) efficiency model research. A comprehensive model is proposed and tested on a self-developed HMT, covering all operating conditions. The model consists of two components: hydraulic and mechanical. The hydraulic model is a semi-empirical approach based on the mechanism of efficiency losses and pump-motor test data, which enables accurate calculations under various conditions. The mechanical model combines a rigid body framework, load dynamics, and transmission loss models to precisely capture transient gear efficiency. This integrated approach facilitates early-stage transmission evaluation, identifies primary loss sources, and assesses efficiency not only in steady-state but also throughout driving cycles.