The invention discloses a temperature field calculating method of an underground power distribution room. The temperature field calculating method comprises the steps that according to heat transfer coefficients of elements in a transformer and the heating power of the elements, an internal temperature field is established by utilizing a finite element analysis method; according to the air velocity and air heat transfer coefficient of the underground power distribution room, a space temperature field of the underground power distribution room is established by utilizing a computational fluid mechanics method; according to convection transfer of the transformer and surrounding air and heat radiation of an iron core and a winding surface in the transformer, boundary conditions of the temperature field of the underground power distribution room are established; an equation set is established according to the internal temperature field of the transformer, the space temperature field and the boundary conditions, and the temperature field of the underground power distribution room is formed. The reliability and accuracy of heat monitoring and fault analysis of the underground power distribution room can be improved by adopting the temperature field. The invention discloses a temperature field calculating system of the underground power distribution room. The system has the above advantages.