The invention provides a QoS guarantee method for achieving distribution network automation service. The method comprises the following steps: receiving a service guarantee request initiated by the distribution network automation service, wherein the service guarantee request comprises a service type, an evaluation index corresponding to the service type and a QoS target demand corresponding to the service type; establishing a linear space corresponding to the service type, and transforming the linear space to obtain a standard linear space corresponding to the service type; establishing a network capacity curved surface of a broadband wireless public network and a QoS demand vector corresponding to the service type; and if the QoS demand vector corresponding to the service type is beyond the range of the network capacity curved surface corresponding to the service type, adjusting the resource configuration of the broadband wireless public network to satisfy the QoS target demand corresponding to the service type. The method is used for providing QoS guarantee for 10Kv and lower middle-lower voltage intelligent distribution network communication servers through the wireless broadband of the public network.