Re: I want to make an interver.output is sinewave,how can I
For low power (< 50W) you can use sinwave generator (eg. ICL8038) and just amplify this signal using linear amplifier and 12/220 transformer connected opposite way around. Tha output will be nice sinewave but unregulated ie. depending on load the voltage may drop 5%...15%....
If your power requirements are higher I would't bother. There is no simple solution and the best you would achieve will be "modified sinewave" which is as bad as square wave. 8)