The dc magnetic susceptibility, linear absorption part of ac magnetic susceptibility and magnetoresistance measurements indicate the appearance of a spin glass state in La0.3Ca0.7MnO3. The nonlinear ac susceptibility X2, X3 and hysteresis curve show that the state in La0.3Ca0.7MnO3 is a reentrant spin glass state. We suggest that an SG state and a ferromagnetic state coexist at 108 K < T < 173 K.