Let L θ be the circular cone in R n which includes second-order cone as a special case. For any function f from R to R, one can define a corresponding vector-valued function f L θ on R n by applying f to the spectral values of the spectral decomposition of x ∈ R n with respect to L θ . The main results of this paper are regarding the H -differentiability and calmness of circular cone function f L θ . Specifically, we investigate the relations of H -differentiability and calmness between f and f L θ . In addition, we propose a merit function approach for solving the circular cone complementarity problems under H -differentiability. These results are crucial to subsequent study regarding various analysis towards optimizations associated with circular cone.