The invention provides a loss calculation method and device and estimation method and device of a dry type smoothing reactor. The loss calculation method comprises the steps of firstly, determining inductance matrix and resistance matrix of the dry type smoothing reactor; secondly, calculating AC-DC distribution of the dry type smoothing reactor; and finally, calculating loss of the dry type smoothing reactor, and estimating the loss of the dry type smoothing reactor. By the loss calculation method, the resistance loss of each layer of winding coil of the dry type smoothing reactor can be accurately calculated, the safety of the dry type smoothing reactor is guaranteed without increasing temperature rising margin and increasing a DC current in temperature rising experiment, the cost increase of an insulation material is prevented, relatively a few wires are needed, the cost is low, and lightness is achieved; and meanwhile, by the loss calculation method, the problems of heat dissipation and temperature rising control of the dry type smoothing reactor in a limited space under a natural circulation condition are solved, so that the accident probability of the dry type smoothing reactor caused by excessively high temperature rising is greatly reduced, and stable, reliable and continuous running of the reactor is ensured.