Students' experience errors in solving proportional problems and prospective teachers' experience were the same thing. Research that explained the wrong strategy for understanding proportional problems still needed to be completed. Objectives to describe the wrong strategies chosen by prospective teachers in solving proportional questions and the resulting answers were evaluated using the SOLO taxonomy and descriptive qualitative approach was applied. 50 prospective mathematics teachers and three subjects as exceptional cases were selected and analyzed further. The proportional reasoning test was used to identify the strategies used by prospective teachers, which consisted of five questions and in-depth observation by conducting interviews from the results of the completed tests. Findings showed that prospective teachers used six wrong strategies in solving proportional problems, namely additive strategies, intuitive, proportional attempt, ignoring data, using number no content, and failing to identify nonproportional problems. The high level of solo taxonomist ability was at the relational level, medium at multi-structural and relational, and low at unistructural and multi-structural. The conclusion showed that the wrong strategies done by student teachers in solving problems was involving proportional reasoning related with the obstacles experienced by prospective teachers in understanding proportions. Further investigation can provide more information on what obstacles are in understanding proportions.