The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy (SEM),Fourier-transform infrared spectrometer (FTIR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) using in-vitro tests.The results show that the soaked fiber is surrounded by an outer calcium-magnesium silicate hydrated layer,and there exists a balancing function between the formation and abscission of the hydrated layer during the dissolution process.The concentrations of leached ions increase constantly,and the mass loss of the fibers and pH changes of the solution are found to rise rapidly during the initial dissolution process,then their increasing rates are controlled by the balancing function of the hydrated layer at the subsequent dissolution stages.The dissolution rate constant and time for complete dissolution are estimated to be 274 ng/(cm2·h) and 15.2 d,respectively,presenting preferable biosolubilities.