This study proposes a comprehensive evaluation system for measuring the difficulty of academic research, focusing on Natural Language Processing as a case study. The authors extract internal and external features from papers, including collaboration, content, and references, to compute multiple difficulty indicators. These indicators are weighted using the entropy weight method and summed to generate a final research difficulty score. Academic impact is quantified by citation frequency, while expert assessments validate the reliability of the measurement approach. Empirical results indicate that page count, reference count, and high-level institutional participation significantly correlate with academic impact. Crucially, the analysis reveals an inverted U-shaped relationship between research difficulty and impact. This suggests that moderately difficult research tends to achieve the highest level of academic influence.