The soot (solid carbon particles) emitted from diesel engines into atmosphere is to consider one of dangerous pollutant because it is easy inhaled deep into the lungs and some polycyclic aromatic hydrocarbons known for their cancer properties are associated with it. The direct gravimetric method is used to measure the soot mass rate. The soot particles through the exhaust pipe are trapped using Pyrex-glass collecting piece with glass wool filter. The rate of soot mass emitted and brake power are expressed in (g/kw hr) unit. The variation of soot mass with engine load is compared with U. S. Environmental Protection Agency (EPA) standards. It is found as the engine load is increased, the rate of soot mass increases and exceeds the (EPA) standards in the first tier. The high rate of soot mass causes strong decrease in the brake power and thermal efficiency. The soot usually burns at the temperature of 600 Co approximately. The results show that the high soot mass in high load can be treated by raising the exhaust temperature and reached to greater than 600Co. In the moderate load up to 70%, it is found that the soot mass emitted is not exceeding the (EPA) standards in the first and second tiers. The exhaust temperature is high and the soot mass rate is to be low and easily treated.