The phase diagram of GdMg(BO 2 ) 5 has been determined by means of XRD and DSC. GdMg(BO 2 ) 5 –NaF system is an eutectic one. The system of GdMg(BO 2 ) 5 –NaF has an eutectic temperature at 1002K and eutectic composition of about 50mass% NaF. Nd 3+ :GdMg(BO 2 ) 5 with dimension up to 17mm×15mm×8mm has been grown from a flux of 15mass% NaF by TSSG method. Nd 3+ :GdMg(BO 2 ) 5 crystal has a FWHM of 7nm at 800nm. The fluorescence lifetime is 38μs. The absorption cross-section and emission cross section are 2.0×10 −20 cm 2 at 808nm and 7.89×10 −19 cm 2 at 1055nm, respectively. This results regards the Nd 3+ :GdMg(BO 2 ) 5 crystal as a potential solid-state laser materials.