  Quantum computer provides new opportunities for quantum chemistry. In this
article, we present a versatile, extensible, and efficient software package,
named Q$^2$Chemistry, for developing quantum algorithms and quantum inspired
classical algorithms in the field of quantum chemistry. In Q$^2$Chemistry, wave
function and Hamiltonian can be conveniently mapped into the qubit space, then
quantum circuits can be generated according to a specific quantum algorithm
already implemented in the package or newly developed by the users. The
generated circuits can be dispatched to either a physical quantum computer, if
available, or to the internal virtual quantum computer realized by simulating
quantum circuit on classical supercomputers. As demonstrated by our benchmark
simulations with up to 72 qubit, Q$^2$Chemistry achieves excellent performance
in simulating medium scale quantum circuits. Application of Q$^2$Chemistry to
simulate molecules and periodic systems are given with performance analysis.
