Abstract: The morphologies of Yb∶YAl3(BO3)4 crystals related to the growth rates(corresponding to the rates of decreasing temperature)are observed.These small crystals were obtained from spontaneous nucleation based on different rates of decreasing temperature.The crystals with the size larger than 2mm have simple morphology composed by ｛1120｝ and ｛1011｝only,which is independent from the rate of decreasing temperature.But the crystals with the size smaller than 2mm have complicated morphologies composed by some rare crystal forms when the rate of decreasing temperature is high.It is reflected that some faces with high surface energy developed in the early growth stage when growth rate is high,but these faces disappeared soon during further growth.That means the crystals grow mainly on the low energy faces:｛1120｝ and ｛1011｝.The surface roughness of the crystals is different,which is corresponding to different growth rates.At high growth rate,the morphologies of ｛1120｝ and ｛1011｝ are changed from smooth to rough,and that of ｛0001｝ keeps rough.From the crystal structure,we qualitatively discussed the Jackson Factor α and the growth mechanisms of these three kinds of faces.