The first B-, V-, R-c - and I-c -band light curves of CSS J022914.4+044340 are presented and analyzed. It is found that CSS J022914.4+044340 is a low mass ratio (0.198 +/- 0.005) deep (63.7 +/- 7.9%) contact binary, indicating that it is already at the end evolutionary stage of tidally-locked evolution via magnetized wind. Because of the totally eclipsing character, the photometric solutions are reliable. The temperature and metallicity are determined from the spectroscopic data as T = 5855 +/- 15 K and [Fe/H] = -0.842 +/- 0.031, respectively. Based on the parallax of Gaia EDR3, the physical parameters of CSS J022914.4+044340 are estimated as M-1=1.44(-0.22)(+0.25)M(circle dot) , M-2=0.29(-0.05)(+0.05)M(circle dot) , R-1=1.26(-0.06)(+0.08)R(circle dot) , R-2=0.65(-0.04)(+0.03)R(circle dot) , L-1=1.718(-0.191)(+0.186)L(circle dot) L-2=0.416(-0.050)(+0.039)L(circle dot) . Combining the fraction of light from the third body via the photometric solution (54%), the luminosity of the third body is estimated as 2.705 L (circle dot). The third body may be inferred to be a subgiant. Thus, why the primary component of CSS J022914.4+044340 has higher mass compared to similar systems is explained, as well as why its metallicity is so poor.