a b s t r a c tA highly accurate approximation for the coefficients of the series expansion of the solution of Laplace's equation around the singular vertex, which are called the generalized stress intensity factors (GSIFs), is obtained by One-Block Method. The method is demonstrated for the slit problem, which has a strong singularity, and for the popular problem on an L-shaped domain. Furthermore, the extremely accurate series segment solution for each of the problems is obtained by taking an appropriate number of calculated GSIFs. Numerical results are presented through tables and figures.