Acoustic metasurface has attracted increasing attention due to the ability of manipulating the transmitted and reflected phase of waves to generate various acoustic functionalities with planar layer of sub-wavelength structure. We design an acoustic metasurface with a semi-closed and nested slotted tube array,and it possesses the capacity of modulating the reflected phase with sub-wavelength thickness (about λ/23). The reflected phase shifts can be obtained from 0 to 2π by different rotation angles of intal slotted tubes. The theoretical results agree well with the numerical results by a finite element method. The results show that some excellent wavefront manipulations are demonstrated with the phase array by using acoustic metasurface such as anomalous reflection and sub-wavelength flat focusing. The design may offer a path for acoustic manipulation and promote the potential applications of acoustic metasurface in low frequency noise control,acoustic imaging and cloaking.