An attempt has been made to estimate the indentation cracking process from the information of acoustic emission monitoring. The relations between crack propagation velocity and acoustic emission threshold in terms of double torsion testing were first investigated. The results indicated that the crack propagation velocity was approximately proportional to the acoustic emission rate. These relations were applied directly to the analysis of the indentation. Various loading speeds and loading levels were selected. Assuming that the radial crack with semi-circular only occurs during indentation process, the crack length should be given as a function of the acoustic emission rate. From the results of calculating the extent of crack propagation obtained by the acoustic emission counts for the indentation, good agreements were obtained between predicted and measured crack length. Fracture toughness values obtained by these testings were also compared.