We investigate the capability of the Taiji space-based gravitational wave observatory to detect stochastic gravitational wave backgrounds produced by first-order phase transitions in the early universe. Using a comprehens ive simulation framework that incorporates realistic instrumental noise, galactic double white dwarf confusion noise, and extragalactic compact binary backgrounds, we systematically analyze Taiji's sensitivity across a range of signal parameters. Our Bayesian analysis demonstrates that Taiji can robustly detect and characterize phase transition sig nals with energy densities exceeding   ΩPT ≳1.4 ×10-11 approximately   10-3 10-2 to   across most of its frequency band, with strong sensitivity at Hz. For signals with amplitudes above ΩPT ≳1.1 ×10-10 , Taiji can determine the peak frequency with relative precision better than 10%. These detection capabilities would enable Taiji to probe elec troweak-scale phase transitions in various beyond-Standard-Model scenarios, potentially revealing new physics con nected to baryogenesis and dark matter production. We quantify detection confidence using both Bayes factors and the Deviance Information Criterion, obtaining consistent results that validate our statistical methodology.