In vitro pharmacokinetics and transformation products of novel marine fibrinolytic compound FGFC1 were studied. Liver microsomes were prepared by Wistar rats. The liver microsome protein concentration was detected by lowry method. The changes of FGFC1 and its transformation products were detected by HPLC method. The conversion products were analyzed by LC-MS/MS method and 4-phenyl-1,2,3-thiadiazole, deacetylcyclopropionate, phenytoin and ketoconazole are selective inhibitors of different subtypes of the CYP450 enzyme system.The in vitro metabolic half-life of FGFC1 was T_1/2=(96.25±2.3) min, and the intrinsic clearance rate CL_int=(0.072 0±0.001 4) mL/(min·mg).The conversion product of FGFC1 is((2S,3S)-2-((E)-7,8-dihydroxy-4-methylnon-3-en-1-yl)-3,5,8-trihydroxy-2-methyl-3,4,8,9-tetrahydropyrano[2,3-e]isoindol- 7 (2H)-one)(PIO)with a molecular weight of 421.2.The fragments of the FGFC1 conversion product was detected by LC-MS/MS at 463.30[M+C₂H₃N+H]⁺ and m/z 110.90[C₇H₈O+H⁺H]⁺, 215.70[C13H₂₆O₂+H]⁺, 337.00[C₁₈H₂₇NO₅]⁺, 337.00[C₂₅H₃₁NO₂]⁺. Phenytoin significantly inhibited the liver microsomal enzyme system CYP3A4 subtype, and the PIO was reduced with 49.11%. FGFC1 is converted by N-dealkylation reaction, N-oxidation reaction and hydrolysis reaction under the catalysis of CYO450 subtype CYP3A4.