The invention discloses a soft rock tunnel excavation and initial supporting method comprising the first step of determining basic mechanical parameters of surrounding rock; the second step of determining an initial supporting structure of a tunnel: the adopted initial supporting structure of the tunnel includes a plurality of tunnel anchoring supporting systems arranged from rear to front; the third step of performing tunnel excavation and initial supporting construction of the tunnel; the fourth step of performing next section excavation and initial supporting construction of the tunnel: performing excavation and tunnel initial supporting construction on the next section; and the fifth step of repeating the fourth step many times, until all the excavation and initial supporting construction process of the tunnel of the soft rock tunnel is completed. The method has simple steps and is convenient to implement and good in use effect. The deformation of the surrounding rock of a tunnelsidewall in a pull cracking and sliding shear collapse state is analyzed, and the tunnel sidewall asymmetric supporting structure is adopted to effective support the tunnel sidewall, and a tunnel archsupporting system is used to effectively support a tunnel arch, which can effectively control the surrounding rock deformation of the soft rock tunnel arch wall.