我知道如果是这里毕业的phD, 转成H1要照样缴税。那么这里毕业的phD,转成J1还享受免税的treaty 吗？

no. both H1 and J1 for research can get the waive (treaty benefit) onlyif he/she has stayed in China for more than 1 years exactly beforearriving US with that visa. in your case, when you get either H1/J1,you have been US for somewhile. my friend who arrived here as H1 couldnot get this just because he applied H1 from Singapore, not directlyfrom China (so strongly indicated that exactly before his H1, he didnot stay in China for 1 year).

明白了，多谢回答。