Abstract: The change of tumor marker in serum is observed with FDG PET and dynamica observation, which is to monitor the curative effect of patients treated with MLD(Multiple Low Dose) of 188Re-CL58(or 131I-HAbl8). The results show that after treated with MLD-RIT, 18F-FDG concentrated in lesions, evaluated with naked eyes and semi-quantitation method (SUV) is decreased significantly. Compared with larger focusts, micro-metastatic lesions show greater decrease of SUV. In some cases, SUV of the metastases are even brough down to the normal line. MLD 188Re-CL58 affect the immune system positively for it brought down CD3+ cell and brough up the ratio of CD4+/ CD8+, while MLD RIT induced no visible blood toxication. Both of them have no toxic effect on liver and kidney. What's exciting, the MLD did not induce any HAMA during the follow-up period(2 weeks to 6 months). So MLD RIT is efficiency for the treatment of micro-metastasis. MLD RIT partially relief the immune system from suppression, the toxication of RIT is manifested mainly as blood cell inhibition. MLD RIT induced no HAMA (Human Anti-mouse Antibody) generally.