Science essences are product, process and scientific attitude. As a process, science is a used procedure to study the object of study, to discover and to develop science products. It seems that Indonesian education is not focusing on developing students' science process skills. Therefore, the researchers employed a problem-based learning model through an authentic assessment based practicum to improve students' science process skills. A Quasi experimental design with pretest-posttest nonequivalent control group design was applied in this study. Biology educational students of STKIP Persada Khatulistiwa Sintang, West Borneo, Indonesia were taken as the population. The participants of the research were 60 students from two classes of animal physiology, each class consisted of 30 students. Essay test was applied to measure the science process skills. Essay test questions cover both science basic process skills and integrated science process skills. The research result showed that problem based learning through practical and authentic assessment affected the students' science process skills and there were significant differences between the problem-based learning model through authentic assessment based practicum with problem-based learning model.