Summary: Symmetries and group invariant solutions to the Gardner-KP equation are obtained by using the direct symmetry method. At the same time, we find the corresponding Lie algebra, optimal system, classification and all similarity reductions. Our exact solutions generalize the corresponding results obtained by A.-M. Wazwaz
[ibid. 204, No. 1, 162–169 (2008; Zbl 1159.35432
)]. In addition, the conservation laws of Gardner-KP equation are also given.