The purpose of this paper is to explain the results of the study of the possibility of applying the Modified Conceptual Understanding Layer Pirie-Kieren-Sagala (PKS) Model as an alternative assessment tool. This literature research uses research subjects in the form of several articles which have been published in various scientific journals. Five articles have been selected, compiled, compiled, reduced, classified and concluded according to the assessment model proposed. The articles focus on learning the PRAKTAK model, the results of the HOTS type problem solving and the conceptual understanding layer. The results of the analysis show that the subjects in the six research results reached a score of 0, 1, 2, 3, 4, 5, 6 and 7. Therefore, the Modified Conceptual Understanding Layer "PKS" Model can be applied as an alternative assessment of the mathematics learning outcomes of HOTS type problems. The indicators of each layer of understanding can be used to differentiate the fulfillment of the learner's understanding layer, with seven scoring scales.