万有引力常数G是物理学中最早为人们所认识的重要基本常数，但其测量精度至今不能令人满意。本项研究拟采用扭秤周期法，并通过考虑最佳配置设计、扭丝滞弹性修正以及克服扭秤和引力场的非线性效应，预计可将G的测量精度提高到50ppm的国际领先水平。在相关引力理论研究方面着重寻找新的物理效应，为今后的引力实验和天文观测研究提供理论基础。.

An accurate knowledge G is not only important from the point of view of.theoretical physics, but also significant for practical purposes. Based on the recent.measurements, in 1999, the Committee on Data for Science and Technology.(CODATA) gave a new recommended value for G, i.e. CODATA-98. It is noted that.the new recommended CODATA-98 value for G is essentially the same as the.CODATA-86 value but the relative uncertainty placed on this value has been.expanded to 1500 ppm. This situation, with a disagreement far in excess of the.estimate, suggests the presence of unknown systematic problems. It means that the.high precision experiments for determining the gravitational constant G and.investigations on all kinds of systematic errors of the different methods are desirable..Based on the research works about the period fitting method and the physical.properties of the torsion pendulum, Newtonian gravitational constant G is determined.by the time-of-swing method with four attracting masses configuration.