<p>Promoting the water retention capacity of soils has become an emerging and crucial topic, both for agricultural farming and mitigating the impact of extreme climate. In this study, bio-hydrogel and microbially induced calcium carbonate precipitation (MICP) were used to treat sand through small-scale box tests. The water retention capacity and surface strength of the treated sands were investigated, considering the effects of superabsorbent polymer (SAP) type, SAP content, biotreatment level, and biotreatment strategies. The test results show that the water retention capacity of the SAP-treated sands can be significantly improved with the addition of SAP. MICP further improves the water retention ability of SAP-treated sands, but its effectiveness depends on the MICP treatment strategies. Soil surface strength can be improved with the addition of SAP and be further enhanced with MICP treatment. With MICP treatment, the morphology of xanthan gum (XG) bonds can be changed significantly. The mixture of XG and CaCO₃ forms a structure with abundant pores. The XG and CaCO₃ crystals can be distinguished or can be seen as a compound in the specimens when different biotreatment methods were used. The porous structure gives a potential explanation for the improved water retention of the SAP-treated sands. This study provides valuable insights into the improvement of soil water retention and soil strength and verifies the potential applications of bio-hydrogel and MICP in both agriculture and environmental conservation fields.</p>