Objective To investigate the feasibility of gastric emptying measured by ultrasonography in guiding enteral feeding in critically ill patients receiving mechanical ventilation. Methods A total of 76 critical patients who received mechanical ventilation for over 24 h and underwent enteral nutrition admitted in our department between May 2014 and November 2015 were recruited in this study. These patients were prospectively randomized into ultrasound assessment group (n=38) and gastric fluid withdrawing group (n=38). The therapeutic strategy of enteral nutrition was adjusted based on gastric emptying and gastric motility index measured by ultrasonography every 4 h for the patients from the former group, while was based on the gastric residual volume by withdrawing gastric fluid every 4 h for those of the latter group. The time of reaching 80% total enteral nutrition (TEN), incidence of ventilator-associated pneumonia (VAP), numbers of reflux and diarrhea, serum level of prealbumin, time of weaning, and length of stay in ICU were recorded and compared for the efficiency of enteral nutrition. Results The time of reaching 80% TEN was significantly shorter ［(36.4±6.2) vs (45.1±7.8) h, P<0.05］, and the incidences of VAP (13.2% vs 36.8%) and of enteral nutrition related complications (28.9% vs 55.3%) were significantly lower in the ultrasound assessment group than in the gastric fluid withdrawing group (P<0.05). What’s more, the time of weaning ［(3.6±1.1) vs (5.8±2.0) d］, and the length of stay in ICU ［(9.2±2.6) vs (12.3±3.7 d)］ were also obviously shorter in the former group (P<0.05). Conclusion Ultrasonography-measured gastric emptying is optimal in guiding the therapeutic strategy of enteral nutrition for the critical patients receiving mechanical ventilation, in improving the efficiency, reducing the related complications, and shortening the durations of ventilation and ICU staying.