The invention discloses a value calculating method of a thermal residual stress of a fiber reinforced composite material under a low temperature. The method comprises the following steps of a, based on fiber random distribution, constructing a representative volume element (RVE) of a composite material; b, dividing a network for the composite material and acquiring a finite element model requiredby calculation; c, endowing the finite element model to thermal/mechanical performance parameters of a fiber and a matrix material which are related to a temperature; d, adding a periodic boundary condition for the finite element model; and e, applying a temperature load to the finite element model and calculating and acquiring the thermal residual stress. By using the method, operation is simpleand prediction precision is high; the method can play an important role in predicting the low temperature residual stress of the composite material so as to lay the foundation for the application of the composite material in a low temperature field.