The question ‘What is the difference between Systematic Theology and Bible Doctrine?” has as many answers as it does theologians. They usually come close to each other in meaning. I am going to keep it simple as is my custom.
Bible Doctrine is about the Bible. That seems easy because it is. What I am saying is all Bible Doctrine is found in the Bible usually hard set.
Systematic Theology (the systematic study of God) does refer to the Bible but also can take information from other places.
The other main difference is the method used to study. Biblical doctrines tend to follow a timeline through history while Systematic Theology usually starts with large ideas and moves to more narrow ideas.
I do hope this simplistic explanation is useful. Please feel free to comment or even suggest a different answer.