To predict the calibration interval of a measuring instrument scientifically, characters of historical calibration data are analyzed, and a combination of GM(1,1) model and Markov method is adopted to acquire the predictive value of calibration data. GM(1,1) model is used to forecast the general trend of the calibration data, and Markov model is used to predict the state of residual series. Experiments are utilized to validate the model. The results demonstrate that the model can well forecast the evolvement of key parameters of a measuring instrument, which means the model is suitable for calibration interval prediction.