Bi4Si3O12 (BSO) is an excellent scintillation crystal,and is becoming the desirable candidate for dual-readout calorimeters in high-energy physics.In this work,high quality BSO crystals are successfully grown by the modified Bridgman method.For the first time,its mechanical and thermal properties are investigated and compared with those of the famous scintillation crystal Bi4 Ge3O12 (BGO).The Vickers hardness and fracture toughness of BSO crystal are higher than those of BGO crystal.Its specific heat,thermal diffusivity and thermal conductivity are measured to be 0.319 J·g-1 K-1,1.54mm2.s-1 and 3.29 W·m-1 K-1 at 298K,respectively.The average thermal expansion coeffcient is calculated to be 7.07 × 10-6 K-1 from 300 to 1173K.Compared with BGO crystal,BSO crystal possesses larger specific heat,thermal conductivity and smaller thermal expansion.These results indicate that BSO crystals possess better mechanical and thermal properties,which will benefit its practical applications.