Objective To evaluate the relationship between hypophosphatemia and prognosis in critically ill patients. Methods Some hypophosphatemia-associated prospective or retrospective clinical cohort studies were searched through CNKI, Wanfang Data, PubMed, Embase, Cochrane library, and Google Scholar English database respectively, with the guidance of these key words such as hypophosphatemia, intensive care, prognosis and fatality rate. The articles were concerned about the correlation between hypophosphatemia and the prognosis of patients in intensive care unit (ICU). The literatures collected were restricted from the creation of data base to April 2017. The mean value of < 0.8 mmol/L in serum phosphorus concentrations of the patients within the first 2 days of ICU admission would be treated as the diagnostic criteria of hypophosphatemia. Literature qualities were assessed by Newcastle-Ottawa scale (NOS). Meta-analysis was carried out by RevMan 5.3, and the sensitivity analysis was performed to test the stability of the meta-analysis. The existence of bias was analyzed by using the funnel graph analysis. Results Ten articles were ultimately included in the analysis, including 9 in Chinese and 1 in English, all of which were high qualities. 1 555 patients were involved in these clinical studies, of whom 606 patients had hypophosphatemia and other 949 were normal phosphatemia. Meta analysis results showed that patients with hypophosphatemia had higher acute physiology and chronic health evaluation Ⅱ(APACHE Ⅱ) score as compared with that of normal phosphatemia group [standardized mean difference (SMD) = 0.64, 95% confidence interval (95%CI) = 0.24-1.04, P = 0.002]. Subgroup analysis showed that APACHE Ⅱ score increased in mild, moderate and severe hyperphosphatemia subgroups, and there were significant differences between any two subgroups (all P < 0.01). Longer duration of mechanical ventilation (SMD = 0.50, 95%CI =0.23-0.78, P = 0.000 3) and the length of ICU stay (SMD = 0.36, 95%CI = 0.06-0.67, P = 0.02), and even higher ICU mortality [odds ratio (OR) = 2.99, 95%CI = 2.09-4.27, P < 0.000 01] were seen in patients with hypophosphatemia as compared with normal phosphatemia patients. However, serum creatinine (SCr) levels (SMD = -0.19, 95%CI =-2.76-2.39, P = 0.89) and serum albumin (Alb) level (SMD = -0.63, 95%CI = -1.54-0.27, P = 0.17) were all similar between hypophosphatemic group and normal phosphatemia group. Sensitivity analysis excluded the effect of heterogeneity on statistical results. The funnel graphics were basically symmetrical, which indicated that the included literatures were distributed well, and the publication bias was small. Conclusions Occurrence of hypophosphatemia in ICU patients is associated with severity of illness, prolonged duration of MV and length of ICU stay, and higher mortalities. Levels of serum phosphorus may have certain clinical values for assessing prognosis of ICU patients.