Hi good day I am working on a BMW 320i out of japan I am getting white smoke and the exhaust is wet what cause it to happen ?the plugs burning white.

SOURCE: 325i BMW emitting white smoke

You are smelling burning antifreeze. likely a head gasket but only testing will determine that for sure...Do not drive it. get it to a shop or more damage is likely.

SOURCE: white smoke from exhaust

If you are getting clouds of white smoke out the exhaust it is a good indicator of antifreeze getting into one or more of the cylinders. I bought a "Great" car sight unseen from a friend once and when he pulled in the drive the whole car disappeared in a cloud of white smoke that only left when he shut the engine off. I found head gasket leaks in half the cylinders. It takes very little coolant to cause the white smoke. If you are absolutely sure of zero coolant loss perhaps the smoke is a little blue--an indication of burning a little oil from a sloppy turbo bearing. Try the nose test-- it may give you the answer. Burning oil has a distinctive smell.

SOURCE: Intermittent white smoke out exhaust and engine misfire

The piston rings in your engine might be needed to be replaced already... go to a local shop with a compression tester.. have your engine tested for compression leaks.. if it does have compression leaks.. then you need to change piston rings. Note** white smokes = engine is burning oil..

SOURCE: White smoke from Exhaust

hardly likely the exhaust job would cause that, but yes it sounds like you got a blown head gasket. badl lock stricks hmm! also preasure test cylinder head for leaks

SOURCE: My isuzu 4JA1 engine tends to exhaust white smoke

White smoke means that you have a coolant leak. Two possible causes for that - either the head gasket is punctured and must be replaced or the head itself is damaged and must be welded by an expert. 
Either way the engine must be dismantled to make a full diagnose and repair.