  We propose a new method to measure parameters of SMBHBs as individual
resolvable evolving single GWs sources, using the timing data of three or more
non-simultaneous pulsars. These parameters include the sky position of the
SMBHB and a chirp mass-red shift combination M_c(1+z). This method requires
both the Earth term and the pulsar terms observed in the power spectra of
timing residuals. The method takes only the frequencies values, thus the
accuracy of parameters estimation is not dependent with SNR nor the form of
timing noises. We applied our method to simulated timing data of three pulsars
to check its validity, the GWs sources location can be constrained with an
accuracy \Delta\Omega~800deg^2, the chirp mass can be determined with a
relative error of ~50%. Our method works better than previous method, when the
size of PTA is small and the SNR of individual pulsar is low, which is likely
the case of near future. In case of large array and how SNR in far future, our
method can provide good prior parameters distribution for Bayesian inference.
