Gastrointestinal tumors, including colorectal and liver cancer, are among the most prevalent and lethal solid tumors. These malignancies are characterized by worsening prognoses and increasing incidence rates. Traditional therapeutic approaches often prove ineffective. Recent advancements in high-throughput sequencing and sophisticated RNA modification detection technologies have uncovered numerous RNA chemical alterations significantly associated with the pathogenesis of various diseases, notably cancer. These discoveries have opened new avenues for therapeutic intervention. This article delves into epigenetic modifications, with a particular emphasis on RNA alterations such as N6-methyladenosine (m6A), 5-methylcytosine (m5C), 1-methyladenosine (m1A), 7-methylguanosine (m7G), and N4-acetylcysteine (ac4C). It examines the functions and mechanisms of action of regulatory entities known as "Writers," "Readers," and "Erasers" to these modifications. Additionally, it outlines various methodologies for detecting these RNA modifications. Conventional techniques include radioactive isotope incorporation, two-dimensional thin-layer chromatography (2D-TLC), mass spectrometry, and immunological detection methods. Specialized methods such as bisulfite sequencing and reverse transcription stops are also discussed. Furthermore, the article underscores the significance of these modifications in the development, progression, and therapeutic targeting of gastrointestinal tumors, including esophageal, gastric, colorectal, liver, and pancreatic cancers. This exploration provides foundational insights for enhancing diagnostic accuracy, treatment efficacy, and prognostic assessment in gastrointestinal oncology.