To improve the accuracy of mediumlong term prediction of satellite clock bias (SCB), a prediction method based on Vondrak filter firstorder differential modified exponential curve model (VDMECM) is proposed. First, the frequent hopping and gross errors phenomenon of SCB before modeling are considers. The median absolute deviation is used to detect and eliminate the clock hopping and gross errors data. Meanwhile, the missing clock data can be recovered by using the Lagrange interpolation method. Secondly, the systematic and random errors of SCB are studied. Vondrak filter smoothing algorithm is used to reduce these errors. Thirdly, the prediction performance of the model is improved by considering effective data bits in SCB. The firstorder difference is used to eliminate the influence of the trend item of the clock bias sequence. And, MECM prediction model is formulated. Finally, the mediumlong term forecast experiments for the next four time periods are implemented based on the postaccuracy precision SCB published in the IGS server. Two typical changing trends are also considered. Experimental results show that the mediumlong term prediction accuracy of this method is better than the quadratic polynomial model (QPM) and the gray model (GM (1, 1)). Compared with these two methods, the average prediction accuracy (RMS) of 60day is increased by 9200% and 8080%, and the average prediction stability (Range) of 60day is increased by 9240% and 8140%.