The writing of multi-layered data bits inside a PMMA block doped with rare-earth ions Ce3+ excited by a 800 nm femtosecond (200 fs,1 kHz, 800 nm) pulsed laser, and the measurement and discussion of absorption spectra and electron spin resonance spectra before and after femtosecond laser irradiation are reported. The results indicate that the block has a low writing energy threshold, and it's propitious to high speed and parallel three-dimensional data storage. Experimental results of three-dimensional recording and reading with 4 μm in-plane pit spacing and 16 μm inter-plane spacing in four layers are presented using a conventional microscope. The relation between the size of the microexplosion pit and the laser pulse energy is discussed. For high storage density, smaller pulse energy is preferable while keeping enough grey value. It's proved that this material can be used in three-dimensional data storage.