This article researched the microstructure evolution of ω and α phase in the solution treatment and ageing process of β-CEZ alloy, which is a kind of typical near-β titanium alloy. The results show that ultrafine athermal ω precipitates (about 1~2 nm) were formed in β-CEZ alloy by quenching from above the β transus temperature. Needle-like α precipitates, about 100nm in length, were formed when solution treated β-CEZ alloy samples were aged at 350℃. The scale of ω assisted α increased to about 200nm in length while increasing ageing temperature to 500℃. The scale of α precipitates grown to about 300nm in length and ω disappeared when the ageing temperature increased to 550℃. Long strip shape α were formed at grain boundaries and the scale of intragranular α increased to several microns when the β-CEZ alloy samples were aged above 650℃.