This study introduce a new frequency parameter calledsfcwt, which can be used to estimate earthquake magnitude on the basis of the first few seconds of P-waves, using the waveforms of earthquakes occurring in Japan. This new parameter is introduced using continuous wavelet transform as a tool for extracting the frequency contents carried by the first few seconds of P-wave.The empirical relationship between the logarithm of tfcwt within the initial 4 s of a waveformand magnitude was obtained. To evaluate the precision of tfcwt, we also calculated parameters tpmax and tc. The average absolute values of observed and estimated magnitude differences (½Mest -Mobs½) were 0.43, 0.49, and 0.66 units of magnitude, as determined using tpmax, tc, and tfcwt, respectively. For earthquakes with magnitudes greater than 6, these values were 0.34, 0.56, and 0.44 units of magnitude, as derived using tpmax, tc, and tfcwt, respectively. The tfcwt parameter exhibited more precision in determining the magnitude of moderate- and small-scale earthquakes than did the tc-based approach. For a general range of magnitudes, however, the tpmax -based method showed more acceptable precision than did the other two parameters.