Mass.gov is a great resource
Check out its "Laws by Source" page http://www.mass.gov/
courts/case-legal-res/law-lib/ laws-by-source/. To find DCF law and regulations, look under the "Massachusetts" heading. Sources of Mass. law are listed in their order of priority - each one of the links there goes to a category of law.
Note that "Regulations" are listed there but policies aren't. That is because regulations have the force of law once they are published in the Massachusetts Record for public comment, then amended based on the comments, then approved by the Secretary of the Commonwealth, then published in the Code of Mass. Regulations. But policies do not.
DCF has an enabling statute, which is Mass. General Laws chapter 18B. Sections 2, 3, and 4 tell them what they can and have to do. Then, Mass. General Laws chapter 119 is about child protection law. It is where the "51A report" and "51B investigation" get their names; i.e., sections 51A and 51B of chapter 119. There are other statutes in which DCF is involved, but these are the two main ones for purposes of this article.
DCF and all state agencies are required to write regulations that expand on and provide specifics about the statutes. You can find DCF regulations at the Title 110 link following the "Code of Massachusetts Regulations" link at the Trial Court Law Libraries "Laws by Source" page to the "Alphabetical list" or the "100-199" to "110"and at DCF's Regulations and Policies page.
Most agencies, DCF included, have policies, which further flesh out the regulations and are what their people are trained to follow. I don't know about other agencies but DCF doesn't put most of their policies on their website. Massachusetts Continuing Legal Education, MCLE®, periodically publishes a manual with a CD including then current DCF policies and the Massachusetts Juvenile Bar Association recently developed a thumb drive that included the regulations and policies, amongst other things; but I am not sure if it is available for purchase. Once you know the name and number of any DCF policy, you can have them emailed or faxed to you by the Mass. Trial Court Law Libraries using their Document Delivery Service.
At the DCF Regulations and Policies page you will notice that there are also "Proposed Amendments" to a few regulations and a few policies. But, the proposed amendments to effectuate the, most relevant, 2/28/2016 "Protective Intake Policy" and the 2/17/2017 "Family Assessment and Action Planning Policy" are not there. Those regulations, though they have already been written and open to public comment, for some stupid reason, are published at a link in the "News" section of the top page of DCF's website - "Regulation Review: Proposed Changes to DCF Regulations". They seem to be pretty close to final so I don't know what they are waiting for to add them to the actual Regulations page.
If you are involved in an investigation, assessment, or case with DCF, always talk to your attorney about which constitutional provisions, statutes, regulations, court rules, or policies affect your case. Feel free to use the Web Resources page of my main website for the links in this article and others, which you may find useful in your DCF or child protection law research. Read my Initial Consultation Policies page if you need to consider retaining counsel for your DCF matter.