Field tests were carried out to observe surface deformation induced by twin shield construction in silty fine sand stratum, based on the project of Nantong Metro line 2. The applicability of the twin peck formula for silty fine sand stratum is examined through measured data, and the value of the ground loss rate and the width parameter of the preceding tunnel and the rear tunnel was analyzed. The results show that in silty fine sand soil, the secondary perturbation effect of tunnel construction on the rear tunnel induces a significant increase in surface settlement above the axis of the preceding tunnel. The secondary perturbation effect in silty fine sand stratum is more obvious than other soft soil stratums, but less than the sand stratum. Compared with silty soil stratum,the impact of shield stoppage on ground settlement is more remarkable in silty fine sand stratum. The ratio of ground loss rate η1/η2 caused by the twin shield construction ranges from 1 to 5 with a mean value of 2.3, and the ratio of the surface settlement trough width parameter K1/K2 between the leading tunnel and the trailing tunnel ranges from 1 to 2 with a mean value of 1.4; The ratios of ground loss rate η1/η2 in sand, silty find sand, and silt soil stratum all exceed 1. Furthermore none obvious relationship can be found between ratios of ground loss rate η1/η2 , width paramete K1/K2 and the ratio of cover depth to diameter (H/D).