We investigated the magnetism of systems Lao.7-xGdxSro.3MnO3 (x = 0.00, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50,0.60, 0.70) by M-T curves, M-H curves, and electron-spin-resonance (ESR) spectra. The experimental results indicate that the system is in a ferromagnetic long-range order at Iow-doping level; the samples of x = 0.30 and 0.40 show cluster-spin glass behaviour: and the antiferromagnetic characters are observed at x ≥ 0.50. For the samples of x = 0.30 and 0.40, the ESR spectra demonstrate that the phase separation occurs above the Curie temperat ure.