Objective. To study a correlation between the values of thrombodynamics parameters of hypercoagulation measured by the thrombodynamics test and the severity of catatonia in children with infantile psychosis in childhood autism (F84.02). Material and methods. Twenty-four patients (22 boys and 2 girls) aged from 3 to 13 years, were studied. The severity of catatonia was determined by BFCRS. A thrombodynamic test was performed in platelet-free plasma using the analyzer T-2 Thrombodynamics Device (Hemacore LLC, Russia). Results. Thrombodynamic (TD) parameters of clot growth rates from the activator (V, Vi and Vst) were statistically significantly higher than normal values. Similar results were obtained for Clot Size at 30 min (CS, μm): Tlag and D values were within normal limits. The values of Time of appearance of spontaneous clots (Tsp min) were less than the lower limit values for the norm (30 min). Correlation analysis showed that the severity of catatonia is positively correlated with the initial clot growth rate (Vi) (p=0.009) and negatively with Tsp (p=0.002). With an increase in the time of appearance of spontaneous clots (due to a decrease in the procoagulant activity of platelet microparticles in the plasma of patients), the severity of catatonia in children with ASD decreases. Conclusion. The results suggest that normalizing plasma and platelet hemostasis is important for increasing the effectiveness of treatment of patients with ASD with catatonia.