The invention provides a method for access network selection according to real-time network conditions, and relates to a network selection optimization method for a heterogeneous network. The heterogeneous network is a network comprising a cellular network and a WLAN, the cellular network is a first network, and the WLAN is a second network. When the service of the first network to which equipment joins is not satisfactory, according to a network list provided by ANDSF and RAN Rules, the equipment offloads the traffic from a top network, and when the load of the first network is too high, or the first network is congested, the equipment can timely switch to the second network. Through adoption of the method, a shortcoming that a better network cannot be selected timely is improved, the network performance is improved, and the resource utilization is maximized.