To provide a composition for a heat cycle system, which comprises a working fluid for heat cycle which has a low global warming potential and high stability, and which can replace R410A, and a heat cycle system employing the composition.
A composition for a heat cycle system, which comprises a working fluid for heat cycle containing trifluoroethylene, and a stabilizer for preventing deterioration of the working fluid for heat cycle, such as an oxidation resistance-improving agent, a heat resistance-improving agent or a metal deactivator, and a heat cycle system employing the composition for a heat cycle system.