Glasses in the system [wt%: (55-x)% SiO2-(15+x)% B2O3-15% P2O5-10% Na2CO3-5% Fe2O3] where 15 ≤ x ≤ 40 % have been prepared with the different amount (35-55 wt%) of boron oxide. The compositions were limited by fixing the P2O5 at 15 wt%, Na2CO3 at 10 wt% and fixing the Fe2O3 at 5 wt%. The objective of this study is to determine the effect of boron oxide on phosphate ion released from borosilicate glass in seawater. The glass has been prepared by melting in the alumina crucible within 2 hours of soaking time at 1300 °C in the furnace and cooled to room temperature. The obtained glass was crashed and sieved with yielding a mean size of 710 μm. The samples were immersed in seawater under dynamic condition by stirring at 310 rpm. The water sample was taken 6 times at every 15 minutes until 75 minutes and analyzed using Discrete Auto Analyzer. The functional group and morphological characterization on the glass surface have been investigated using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). Analysis of the data indicates that the amount of 50 wt% boron was the best and optimum for the phosphate ion release which is 126.53 ppm.