The co-combustion behaviors between sewage sludge and oil shale were investigated in this study. The TGA experiment was given a temperature spanning from 105 degrees C to 1000 degrees C by setting the heating rates 10, 20 and 30 degrees C/min. The combustion characteristics, characteristic index, co-combustion interactions, activated energy and DAEM of blends were studied in this paper. The ignition temperature shifted to an earlier temperature when adding sludge. An inhibition interaction of co-combustion occurred at low temperature and the proportion of sludge with 10% showed the best promoting effects. The average activated energy reached the minimal also when the ratio of sludge was 10%. The average fractional residuals were less than 1.3%. Models showed a good recuperation with experimental data.