The invention discloses a method for determining crack initiation toughness of concrete by a two-point method of lines. The method comprises the following main steps: fabricating a set of test pieceshaving completely the same size, performing static loading to obtain a crack initiation load, determining a line by two points and obtaining the slope of the line, wherein the slope is the crack initiation toughness of concrete free of size effect. The method avoids fitting analysis of a number of experiment data, approaches factors from all angles, is enough precise in prediction results, and iseasy to determine result rationality.