Photocatalytic　ammonia　synthesis　is　another　important　reaction　to　mimic　natural　nitrogen　fixation,　which　has　attracted　more　and　more　attention.　In　recent　reports,　sacrificial　agents　are　often　used　to　promote　charge　separation,　and　high-activity　photocatalysts　are　discovered　by　using　Nessler＇s　reagent　method　as　a　detection　technique　of　ammonia　production.　However,　there　is　an　open　question　on　the　rationality　and　accuracy　of　the　ammonia　production　amount　in　the　presence　of　the　sacrificial　agent　and　Nessler＇s　reagent　detection　method.　In　this　report,　P25　TiO2　is　employed　as　a　model　photocatalyst　and　alcohol　as　sacrificial　agent,　and　both　Nessler＇s　reagent　and　cation　exchange　chromatography　are　employed　as　ammonia　detection　methods.　The　different　ammonia　production　amount　was　found　by　the　different　detection　method.　HPLC　and　H-1　NMR　results　indicate　that　carbonyl　compounds　(formaldehyde,　acetaldehyde,　and　acetone)　are　produced　in　the　reaction.　When　the　carbonyl　compound　was　added　to　the　ammonia　standard　solution,　the　interference　effect　on　the　detection　of　ammonia　was　found　in　the　Nessler＇s　reagent　method.　No　interference　effect　was　found　in　the　cation　exchange　chromatography.　Thus,　the　Nessler＇s　reagent　is　not　suitable　for　ammonia　detection　in　the　presence　of　alcohol　as　the　sacrificial　agent.