本文从ＢａＢ２Ｏ４Ｎａ２Ｏ赝二元体系的相图和杠杆原理出发，研究了助熔剂提拉法生长βＢａＢ２Ｏ４（ＢＢＯ）晶体的等径条件，得出了生长过程中降温速率的数学表达式，解释了助熔剂法生长晶体出现缩径的实验现象，为进一步提高等径生长ＢＢＯ晶体的质量提供了理论依据。 Based on the phase diagrams and the lever principle of the BaB2O4-Na2O pseudo-binary system, the isobaric conditions for the growth of βBaB2O4 (BBO) crystal by flux pulling were studied. The mathematical expressions of the cooling rate during growth were obtained, The experimental phenomenon of diameter reduction of flux grown crystals was explained, which provided a theoretical basis for further improving the quality of the as-grown BBO crystals.