We find a easy and exact way to solve the eigenvalues of a optical microphere resonator.According to the eigenvalue's equation derived the characteristics of WGM when light coupling from fibers into microsphers,we got the eigenvalues by constructing figures of the function in the eigenvalue's equation.Contrasting to the datum observed in the experiment,we can find that the relative error is ess than 0.1%.Comparing with the method of common formula,our result is more accurate,and the method is much more convenient.