Most of the previous work focused on fire behavior of non-combustible construction. However, few investigations have systematically addressed fire development and window ejected flame based on large-scale light timber frame construction (LTFC). This paper conducted a large-scale natural fire experiment to explore the fire development of wooden buildings and the ejected flame behavior by a two-layer light timber frame construction (LTFC). The experimental LTFC included two compartments, with four façade walls consisted of external and internal linings, within 5.1 m height, 3.6 m long and 2.4 m width, and weight of 1480.1 kg. The room temperature, mass variation in burning, radical temperature profiles outside the openings-façade wall, and ejected flame dimension were measured and analyzed. The results were summarized as follows: In LTFC, the room temperature and heat release rate (HRR) would show a second rapid rise, as if “twice flashover” occurred in fully burning stage. This phenomenon is obviously different from the traditional compartment fire development of buildings. Besides, after flashover, the ejected flame height continuously increased until the fire turned into decay stage, whereas the horizontal ejection distance would maintain a steady stage and increased as the openings broken extremely. Furthermore, the region outside the openings façade wall could be divided into three regions, ejected flame region (including continuous and intermittent flame) (Tr > 180 °C), buoyant plume region(150 °C > Tr > 60 °C) and heated air region(60 °C > Tr > T8). A modified function was proposed to predict the temperature profile at different heights for the openings-ejected flame. The data of this paper will enhance the comprehension for fire development of timber buildings and provide some useful information to assess the thermal behavior of window-ejected flame of façade wall.