Digging Phascolosoma esculenta to increase income is one of the main causes leading to the degradation of China mangroves. In order to understand the impact mechanisms of digging P. esculenta on the mangrove growth and to select indicators to evaluate the mangrove health, a simulative study was conducted to clarify the impacts of digging depth, radian, and frequency on the growth of 1-year old Avicennia marina seedlings, with the indices seedling height, basal diameter, single leaf area, specific leaf area, total biomass, and dead root dry mass measured. The results showed that digging activities decreased the increment of seedling height and basal diameter, single leaf area, specific leaf area, and total biomass significantly, and increased the dead root dry mass markedly. Digging depth and radian had obvious effects on the growth of A. marina seedlings, but digging frequency had minor effects. When the digging depth was < 5 cm, digging radian was < 240 degrees, and digging frequency was < 2 times per month, the damage to the seedlings was slighter; but when the digging depth was > 5 cm, the damage was quite serious.