Based on the theory of r.f. SQUID,the principle for a phase-sensitive test of the symmetry of the order parameter in high-temperature superconductors by using r.f. SQUID in the inductive mode(β≤1,without the limit of β1)is given.We also investigate (calculating and discussing) a system with β=0.7 and offer the range of its r.f. bias flux,under which the r.f. SQUID can be used to probe the phase of the pairing state.