This paper describes a curriculum-based multidimensional computerized adaptive test that was developed for Indonesia junior high school Biology. In adherence to the Indonesian curriculum of different Biology dimensions, 300 items was constructed, and then tested to 2238 students. A multidimensional random coefficients multinomial logit model was used to develop multidimensional scales. A simulation study based on the item and ability parameters estimated from real data is conducted to evaluate the performance of the proposed Biology-MCAT system. The results show that the bias and standard error of Biology-MCAT system are acceptable. It suggests that, this online assessment system can be a model for Indonesian National Examination in future.