Abstract: In order to improve the effect of enzyme induced carbonate precipitation (EICP) in solidifying subground soil, this study proposed a technique of hydroxyethyl cellulose (HEC) combined with EICP to solidify silty sand, and analyzed the water stability of treated silty sand. The surface strength and water stability were taken as the investigation indexes (water stability was evaluated by disintegration rate and strength loss rate after immersion). Four factors (HEC concentration, spraying amount, spraying times, calcium source concentration) and four levels orthogonal test were carried out. The solidified mechanism was analyzed from the perspective of macro and micro through micro penetration test, disintegration rate determination test, strength loss rate after immersion determination test and micro experiments.The results showed that fro different evaluation indicators, HEC concentration ranked first in the primary and secondary order of each factor’s influence. The optimal solidification parameter for HEC combined with EICP to solidify silty sand is HEC concentration of 0.6 g/L, spraying amount of 3 L/m², spraying frequency of 4, and calcium source concentration of 0.75 mol/L. At this time, the surface strength of solidified silty sand is increased by 57.47% compared to that of traditional EICP, and the disintegration rate and strength loss rate after immersion are 78.64% and 83.75% lower than those of traditional EICP, respectively. The incorporation of HEC changed the single cementation mode of EICP, generating "wrapping" and "connection" effects between soil particles, forming a chain network structure of soil particles-HEC-CaCO₃, which improves the surface strength and water stability of silty sand.