The invention discloses a method for calculating full-age compressive strength of underground construction concrete. The method comprises the following steps of (1) carrying out analysis and calculation to determine a design-age compressive strength of concrete; (2) calculating a 28d-age compressive strength of the concrete; and (3) calculating a full-age compressive strength of the concrete. The method disclosed by the invention is simple in calculation formula, is based on statistical analysis of more than 250 fly ash concrete compressive strength test results of a large number of practical underground constructions, is capable of reasonably reflecting a relationship between compressive strength of underground construction concrete and the age, a relationship between typical-age compressive strengths and the influences of fly ash replacement, is capable of rapidly calculating the full-age compressive strength of the underground construction concrete in high precision, and completely can be applied to the design calculation, safety evaluation and service life research of practical constructions, the research of influences of the fly ash replacement, and especially the preliminary design and on-site real-time calculation analysis.