OBJECTIVE To study the pharmacokinetics of nasal tetramethylpyrazine phosphate (TMPP) pH-sensitive in situ gel in rat blood and brain. METHODS After intranasal administration of TMPP pH-sensitive in situ gel and TMPP solution respectively in rats, microdialysis was used to collect brain and blood samples simultaneously. The concentration of TMPP in the sample was measured by HPLC. Main pharmacokinetic parameters were calculated by Kinetica 4.4 pharmacokinetic software. RESULTS The concentration-time curves of the two preparations fitted to two-compartment model. The main pharmacokinetic parameters of TMPP pH-sensitive in situ gel and TMPP solution in blood and in brain were as follows： in blood： t_max (15.0±1.0) and (35.0±1.0) min; ρ_max（5.857±1.3）and（5.848±1.0）μg·mL^-1；AUC_0～∞(529.9±68.6) and (642.7±54.3) μg·mL·min^-1, respectively. In brain： t_max (15.0±1.0) and (35.0±1.0) min; ρ_max（7.134±0.8）and（6.738±1.1）μg·mL^-1；AUC_0～∞(615.4±71.2) and (801.4±67.5)μg·mL·min^-1, respectively. CONCLUSION TMPP in the pH-sensitive in situ gel can be easily absorbed and transferred into brain after intranasal administration, and the gel shows sustained-release effect.