The accurate measurement of coal seam gas content is essential for several aspects of deep coal mining, including disaster management, resource allocation and sustainability. However, obtaining in-situ coal samples while preserving gas content under challenging conditions, such as high stress, temperature fluctuations, and drilling fluid environments, remains a significant challenge. To overcome this difficulty, we present an innovative in-situ pressure- and gas-preserved coring tool specifically designed for deep coal mining applications. This device enables the collection of coal seam samples under in-situ conditions while ensuring that both pressure and gas content are preserved, thereby preventing gas escape during sample transfer and providing more accurate parameters for evaluating coal and natural gas reserves. In the demanding environment of deep coal seams, the performance of the pressure-preserved chamber of the corer relies on the reliability of its remote triggering mechanism. The presence of drilling fluid introduces medium resistance, which can impair the triggering process–an issue largely overlooked in previous research. Herein, we propose a robust method to calculate remote triggering forces within liquid media and optimize its key parameters to improve operational stability. Laboratory tests and field validations in coal mining environments are conducted, which confirm the effectiveness of the optimized design and demonstrate the tool’s practical applicability. This study offers valuable insights into addressing key challenges in deep coal reservoir exploration and gas resource preservation.