[3] Koychev studied civil engineering and architecture at Ghent University in Belgium under Louis Cloquet and graduated in 1901 with honours.

He taught at the National Academy of Arts (1910–1914) and at the Sofia High School of Technology (1914–1917).

The Neo-Byzantine Pleven Mausoleum draws inspiration from medieval architecture, while the Pazardzhik post office and the Tsarska Bistritsa palace are based on the vernacular style of the Bulgarian National Revival.

His later works like the court houses in Sofia and Ruse are more strictly classical, austere and monumental.

[5] Koychev himself considered his career to have started with his favourite work, the mausoleum in Pleven, and to have ended with his most grandiose design, the court house in Sofia.