Heartbeat interval time series is an example of natural signals with 1/f characteristics. The exponent α of the 1/fα spectrum has some clinical significance. But sometimes the 1/f components is superimposed by some sinusoid components in the signal. To estimate the slope accurately, the 1/f component must be extracted from the signal. The singular spectrum analysis (SSA) method is recruited here to perform the task. Experimental results on data from real patients are satisfactory.