Abstract: Background Heat-related illnesses, particularly heatstroke, are one of the most common environmental emergencies. Insufficient protective measures lead to elevated incidence rates, and delayed diagnosis and treatment may induce exertional heatstroke, which carries an extremely high fatality rate, adversely affecting patients' physical and mental health and threatening their lives. Objective To evaluate and synthesize the best evidence for on-site first aid measures for heatstroke in field/combat environments, thereby informing the development of clinical protocols for heatstroke management, transportation, and emergency interventions in such settings. Methods A systematic search was conducted across multiple databases, including CNKI, VIP, Wanfang Data, CBM, PubMed, Elsevier ScienceDirect, SpringerLink, and ProQuest Health & Medical Complete, to identify evidence on heatstroke first aid measures in field environments. Eligible sources included guidelines, clinical decisions, expert consensus statements, systematic reviews, and meta-analyses published through December 31, 2024. Two researchers independently appraised the quality of included literature and extracted evidence. Results Sixteen articles were included, comprising 1 clinical practice guideline, 10 expert consensus documents, 2 systematic reviews, 2 meta-analyses, and 1 evidence summary. A total of 32 evidence-based recommendations were synthesized across five domains: preventive measures, rapid identification and assessment, active cooling strategies, adjunctive interventions beyond cooling, and medical evacuation and transportation. Conclusion This evidence synthesis offers guidance for pre-hospital emergency personnel in managing heatstroke in field/combat environments. Implementation of these recommendations may enhance clinical outcomes, reduce complications, and lower mortality rates among heatstroke patients in military or austere settings.