This study aims to determine students' learning difficulties on tissue culture materials at the State University of Medan from cognitive aspects based on Taxonomy Bloom, learning indicators and factors causing student learning difficulties. The type of research used is field research. The population of this study is Biology's bachelor students degree who are conducting subjects Tissue culture in bachelor degree of Biology Education Program in State University of Medan. Samples are taken by using purposive sampling which are consisting of 3 classes. Technique of collecting data used is test result of student learning on tissue culture and questionnaire of learning difficulties. The results shown the percentage of students' learning difficulties at the level of knowledge (C-1) is 30.42%, the level of understanding (C2) is 60.02%, application level (C3) of 60.64%, level of analysis (C4 ) is 59,73%, level of evaluation (C5), and level of creation (C6) is 61,38%. While the percentage of student's learning difficulties from learning indicator aspect in indicator-1 that is 48,43%, the 2nd indicator that is 69,24%, 3rd indicator is 72,63%, indicator 4th is 69 ,09%, 5th indicator is 36.22%, 6th indicator is 47.18%, 7th indicator is 67.40%, 8th indicator is 35.43%, indicator 9th is 52 , 17%, the 10th indicator is 25.20%, the 11th indicator is 55.12%, the 12th indicator is 52.95%, the 13th indicator is 60.63%, the 14th indicator is 49 , 21%, the 15th indicator of 62.40%, the 16th indicator of 53.54%, and at the 17th indicator of 39.96%. The causing students' learning difficulties supported the tissue culture materials ; psychological factors, interests, motivation, teaching methods, teaching media, sources / books used in learning, experience, influence of friends, and role of parents.