Wash soybeans, almonds, and walnuts thoroughly and soak them for at least 8 hours.
Drain the soaked soybeans, almonds, and walnuts, and rinse them again.
Put the soybeans, almonds, walnuts, and water into a blender and blend until smooth.
Strain the mixture through a sieve to separate the soy milk.
Pour the strained soy milk into a pot and simmer over medium heat for 10 minutes, stirring constantly.