Juice your oranges until you have 1 cup of blood orange juice.
Stir together the blood orange juice and granulated sugar in a medium saucepan and heat over medium-low heat. Stir until all sugar is dissolved and everything is combined, then remove from heat.
Strain the syrup through a fine mesh strainer to remove pulp, then transfer to a syrup bottle or mason jar and store in the fridge for up to 2 weeks.