The invention relates to a surrounding rock classifying method suitable for milling and excavating of tunnels. The surrounding rock classifying method comprises the following steps: S1. primarily judging primary classification of the surrounding rocks of the tunnels and marking a primary classification sign according to geological conditions, the excavated stable state and velocity of longitudinal wave of elastic wave of the surrounding rocks for the milling and excavating of tunnels; S2. carrying out secondary classification on the surrounding rocks for the milling and excavating of tunnels and marking a secondary classification sign based on the working efficiency of a milling excavating machine; and S3. obtaining potential risk of milling and excavating the surrounding rocks for the tunnels based on the primary classification and the secondary classification and outputting corresponding technical measures. Compared with the prior art, the method is capable of simply, intuitively and accurately reflecting various conditions when the tunnels are excavated by using a milling and excavating method and also capable of providing basis for reasonable classification of the surrounding rocks for milling and excavating of the tunnels; the protective measures can be further adopted conveniently.