The　aim　of　this　study　is　to　investigate　the　relationship　between　green　technology　R　&　D　investment　and　corporate　performance　(ROA)　of　44　Beijing-listed　energy　companies　from　2016　to　2021　using　a　threshold　regression　model.　The　results　show　that　there　is　an　inverse　W-shaped　nonlinear　relationship　between　green　technology　R　&　D　investment　and　firm　performance.　This　means　that　green　technology　R　&　D　investments　only　have　a　positive　effect　on　firm　performance　within　an　appropriate　green　technology　R　&　D　investment　interval,　and　a　negative　effect　occurs　outside　this　interval.　Additionally,　the　study　analyses　the　influence　of　three　threshold　variables　(firm　size,　capital　structure　and　capital　density)　on　the　relationship　between　green　technology　R　&　D　investment　and　firm　performance.　The　results　show　that　firm　size　has　an　inversely-　U-shaped　relationship,　the　capital　structure　has　a　negative　nonlinear　relationship　and　the　capital　density　has　an　inversely　N-shaped　relationship.　Optimal　intervals　are　observed　for　all　three　threshold　variables.　Moreover,　the　study　shows　that　the　green　technology　R　&　D　investment　intensity　has　a　lagged　effect　on　firm　performance.　The　positive　influence　weakens　over　time,　and　the　negative　influence　becomes　more　pronounced.　The　findings　of　the　study　can　help　energy　companies　to　develop　green　technology　R　&　D　innovation　strategies,　such　as　differentiating　green　technology　R　&　D　expenditures　for　companies　in　different　development　situations.　It　can　also　exploit　the　driving　effect　of　green　technology　R　&　D　investment　on　firm　performance　in　the　context　of　China＇s　energy　sector　restructuring.