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In this contribution,the a preformation factors of 606 nuclei are extracted within the framework of the generalized liquid drop model(GLDM).Through the systematic analysis of the ɑ preformation factors of even-even Po-U isotopes,we found that there is a significant weakening of influence of N = 126 shell closure in uranium,which is consistent with the results of a recent experiment[J.Khuyagbaatar et al.,Phys.Rev.Lett.115,242502(2015)],implying that N = 126 may not be the magic number for U isotopes.Furthermore,we propose an improved formula with only 7 parameters to calculate ɑ preformation factors suitable for all types of ɑ-decay;it has fewer parameters than the original formula proposed by Zhang et al.[H.F.Zhang et al.,Phys.Rev.C 80,057301(2009)]with higher precision.The standard deviation of the ɑ preformation factors calculated by our formula with extracted values for all 606 nuclei is 0.365 with a factor of 2.3,indicating that our improved formula can accurately reproduce the ɑ preformation factors.Encouraged by this,the ɑ-decay half-lives of actinide elements are predicted,which could be useful in future experiments.Notably,the predicted ɑ-decay half-lives of two new isotopes 220Np[Z.Y.Zhang,et al.,Phys.Rev.Lett.122,192503(2019)]and 219Np[H.B.Yang et al.,Phys.Lett.B 777,212(2018)]are in good agreement with the experimental ɑ-decay half-lives.