Thank you for all comments above.
Today I try to use ethylene glycol (100 mL) to dissolve 10 mg RhCl3, however, it obviously was insoluble. I do not know that why several people said RhCl3 can dissolve in OHC2H5OH. Please note that Rhcl3 I used at the moment is without any crystal water. Herein, i want to ask the reason to the advisor in the above. Thank you!