I've worked in daycare for 13+ years. It breaks my heart when I'm in the 2 year old room. They are so young and just want their mommies. Some get over there crying in a couple weeks, some a few months.
How long is he in daycare each day, how long has he been attending that daycare and does he have to be there? Two years old is very young and they don't know what is going on. They do not have the maturity or capacity to understand where mom is going and that she is coming back. Separation anxiety is quite common at this age.
You don't mention your working situation or if this is for "socialization". If there is any way to keep him at home either with you, family or a babysitter, by all means arrange that. At this age, kids should be home. At 2, kids do not play with other children, they participate in what is called parralel play/learning. This can be accomplished by taking him to the park or mommy and me outings. Kids do best in preschool when they are older 3, young 4. At this age they are eager to learn and have the concept of parents coming back. Your son has a long school life ahead of him, it doesn't have to start now.
If he unfortuanelty must be in daycare, take a good look at the school. It may not be the right place. Some things to think about the school:
-how many kids to teachers
-are the same teachers there everyday and are they nice
-what kind of activites and opportunities are available or do the kids just play all day
-how involved are the teachers with the children and class activities
-do other kids seem happy and healthy, is there a lot of biting, hitting (more so than usual 2 year old so!)
-how are nap and mealtimes
-cleanliness and diapering procedures
-is the director involved in the school
-how do other parents seem (complaints, happiness, etc.)
-stop by at various times of day to see how things are
Hope these suggestions help.