This study aims to determine the ability of problem-solving and problem-solving patterns based on the level of problem-solving of students through project-based flipped classroom learning. The study used a quasi-experimental design with a one-group pretest-posttest village design. The study was conducted at SMAN 14 Semarang in the academic year 2019/2020 with the research subjects 65 students of class XI MIPA. Samples were obtained through a purposive sampling technique. Data collection techniques are done using tests and interviews. Data analysis of problem-solving ability is done descriptively. The results show that the students' problem-solving ability in project-based flipped classroom learning is relatively high with 57% of students. Students have different patterns of problem-solving based on the level of problem-solving. Very high category students complete the solution by reading, understanding the problem, analyzing, planning a settlement strategy, implementing and evaluating all solutions. High category students do the settlement by reading, understanding the problem, analyzing, planning a settlement strategy, implementing and evaluating mathematical solutions. Low category students do the settlement by reading, understanding the problem, analyzing, determining the problem.