The invention relates to alkaline modified seaweed gel fracturing fluid. The alkaline modified seaweed gel fracturing fluid comprises the following components: 0.20-1.50% of modified seaweed gel, 0.30-1.00% of clay stabilizing agent, 0.30-1.00% of cleanup additive, 0.05-0.20% of bactericide, 0.05-0.15% of demulsifying agent, 0.30-3.00% of crosslinking agent and 0.01-0.10% of gel breaker. The fracturing fluid has low base viscosity and good fluidity and forms a space net structure under the action of the crosslinking agent. The frozen gel can be lifted and hung, is sheared for 60 minutes under the conditions of 80 DEG C, 170S<-1> and 3.5MPa, has viscosity maintained above 60mPa.s, can be thoroughly broken within 2 hours under the action of ammonium persulfate, has gel breaking fluid viscosity less than 4mPa.s, surface tension less than 25mN/m, residue content less than 350mg/L and static sand setting rate less than 0.03cm/min and can meet the construction requirements of non-alkali-sensitive reservoirs within 80 DEG C.