In many practical problems, we must break through the finite interval of integral and the boundedness of integrand function, and consequently we get two forms of improper integrals; the im- proper integral in an infinite interval and the improper integral of an unbounded function. Because im- proper integrals,related to convergence, therefore, the determination of convergence and diver- gence of improper integrals are very important. This work discusses a new logarithmetic criterion for improper integrals, and proves that the new logarithmetic criterion is more precise than the old logari- thetic criteria.