Abstract: A low-cost eco-friendly aqueous foam, especially the robust foam with great tolerance to high salinity and high temperature, is in great demand in the oil industry, e.g., oil and gas well or geothermal well drilling. Herein, an ultra-stable aqueous foam was developed using the biodegradable cellulose microfiber (CMF) as a foam stabilizer. The foam stabilized by CMF shows excellent tolerance to the high concentration of NaCl (6.0 wt%) and CaCl2 (0.25 wt%) and the related drainage half-life times (T0.5) reach 1750 and 2340 s respectively. By contrast, the foams without CMF are completely drained (T0.5 = 0 s) when NaCl concentration is greater than 6.0 wt% or CaCl2 concentration is greater than 0.20 wt%. Notably, T0.5 of the foams stabilized by CMF at these saline concentrations still can maintain above 1000 s even after aging at 120 °C for 16 h, exhibiting an outstanding foam-stabilizing performance at high temperature. Experimental results suggest that the salt and high-temperature tolerance of CMF in foam stabilization is attributed to the electrically uncharged surfaces, the formation of a gel-like structure and the excellent thermal stability. This work not only provides a promising candidate of aqueous foam stabilizer to deal with high temperature and high salinity but also presents a natural-based solution for an environmentally friendly drilling industry in the future.