My daughter's step son who is 12 yrs old is autistic. He likes to sit and watch tv. Is there any good programs for autisic children or any new break?

Depends . Although tv is an easy default for children who may have difficult behaviors it should be limited. There really is nothing positive that comes from watching most television and at best the effect is neutral. Choose shows that have some educational benefit for regularly watched shows and avoid those that promote violence or inapporpriate behaviors. If there is a favorite show use as a reward.
Too much TV not good. Too much tv is not good for any kid wether autistic or not. I would restrict tv and or any electronic gaming to one to two hours per day. Apart from effects of brain learning fast paced movements which can cause major issues with concentration in real life, sedentary life brings on many medical problems with in future. Remember he is not needed social skills or social exposure that is needed for a.