This research investigated the current status that the senior high school mathematics teachers’ understanding of the students’ learning situation after class. A total of 72 senior high school mathematics teachers from four cities in Shandong province participated in this investigation. This research adopted the method of interview and open-ended structure questionnaire to collect information. The results showed that: (1) 69.4% of the senior high school mathematics teachers chose less than 6 students to understand their learning situation; (2) 44.4% of the senior high school mathematics teachers focused on understanding the situation of the middle students’ learning; (3) 66.7% of the senior high school mathematics teachers tended to understand the students’ learning situation just after new class; (4) 44.4% of the senior high school mathematics teachers usually took about five minutes to understand the situation of students’ learning; (5)80.6% of the senior high school mathematics teachers usually understood students’ learning situation though direct requesting and 65.3% of them understood students’ learning situation by looking through their homework and exercise; (6)55.6% of the senior high school mathematics teachers were inclined to understand the contents of the mastery of knowledge. Therefore, the current senior high school mathematics teachers’ after-class understanding of students’ learning situation was obviously unreasonable and not deep enough, which may be one of the reasons why current senior high school mathematics teachers couldn't conduct effective teaching smoothly.