This research carried out blended learning strategy through class action research. The aim of the application of blended learning in class was to encourage the students' critical thinking skill. The application of blended learning strategy was motivated by evidence that the existing strategy leaved the students passive which entailed in the limited materials as given by the lecturers. Blended learning strategy was expected to develop the lecturers' instruction in gaining the learning achievement. The subjects of the research covered 35 students of the Accounting Study Program, University of PGRI Madiun. The research was carried out by three-cycles Class Action Research. The data were taken through the learning activities by means of observation guide, and through students' achievement test. The results showed that the students' critical thinking skill developed after treatment from 8.4% to 42.2% in the first cycle. In the second cycle, it developed even greater to 92.3%. In the third cycle, the students' achievement passed the threshold level. The conclusion was then that blended learning was effective in developing the students' critical thinking skill.