Abstract: By using one-dimensional Chebyshev polynomials expansion, the interpolation experiments of missing data for annual precipitation and monthly mean temperature have been made. A number of tests have been made for the selection schemes of two kinds of critical iteration times and iterative terminal value method of ideal initial values. The results are as follows: the calculating accuracy of the terminal values are higher generally; but the fitting results of ideal initial value much better for dryness-wetness year; the accuracy of interpolation of missing data for year is higher than that for continuous several years; the calculating results of two-direction interpolation method are better than that by using sequential or contrary interpolation alone.