Objective：To study accuracy of 2-D matrix Detector729 in dosimetric measurement and its application in radiotherapy quality control. Methods：Tests and output factor measurement were performed to evaluate and compare the accuracy of Detector729 taking 0.6 cm3 ion chamber under the X-ray as reference. Detector729 was used as a tool to verify dosimetric distribution for inten－sity modulated radiation therapy（IMRT）. Results：The scale factor of Detector729 from the reference ionization chamber was 0.991，and the comparison results showed the maximum deviation of measuring point dose was 0.57%. Meanwhile，under the square fields of 4 cm×4 cm-20 cm×20 cm，the estimated output factor matched very well with the reference ion chamber measurements. Conclusion：With high accuracy and reliability，Detector729 can be used in dosimetric measurement and quality control of radiotherapy and pro－vide theoretical basis for the standard use of radiation dosimetric measurement instruments.