I believe that's a Portulacaria afra; takes care similar to that of Jade plants (tho' this is not a Jade or even a Crassula).

Because the stems are not dark (reddish purple) & the leaves look like they could be alternate on the stem (rather than opposite), I'm going to say it looks like Sedum tetractinum to me. (Chinese Stonecrop) If it is this, it will have yellow, star-shaped blooms. What size are the leaves? It looks like your plant has a trailing habit, but that could be deceptive in the pic. Is it trailing?

I have found pix of older (bonsai) specimens of Portulacaria afra that don't have the dark stems. If it is this, it will have tiny pink blooms.

This is a good example of why it's so important to say where the plant is growing if outdoors. Portulacaria afra is for zones 9 to 11, Sedum tetractinum 5 to 8. Though Sedum may grow in a warmer zone Portulacaria won't grow in colder one.

thanks guys it is Portulacaria afra, its leaf size is smaller than jade plant. at first i thought it was jade plant