Abstract: A method for determining dipropofol in the plasma of Beagle dogs was established by HPLC-MS/MS. We also studied the pharmacokinetic characteristics of two different forms of crystal tablets of dipropofol in Beagle dogs. All animal experiments were approved by the Animal Experimental Management, Welfare and Ethics Committee of Pharmacology Evaluation Research Center, Shanghai Institute of Pharmaceutical Industry. The results indicate that the maximum plasma concentration (C_max) of dipropofol was 69.02 ±20.16 μg·L^-1 after 20 mg·kg^-1 crystal form Ⅰ tablet taken orally, and the AUC_0-t was 160.49 ±55.26 μg·L^-1·h. After 20 mg·kg^-1 crystal form Ⅱ tablet taken, the C_max of dipropofol was 92.58 ±60.26 μg·L^-1, and the AUC_0-t was 243.59 ±148.36 μg·L^-1·h. The AUC_0-t and C_max of crystal form Ⅱ were significantly different from that of crystal form Ⅰ (P<0.05). Crystal form Ⅱ was the dominant crystal form. The results suggest that we should control crystal form during the development of dipropofol oral tablets.