This paper reported the distribution and photolytic rates of cypermethrin, deltamethrin, fen-valerate and trifluralin in soil of different particle sizes. The results showed that soil particle sizehad significant effects on equilibrium amounts and photodegradation half-lives of the pesticides insoil. In two clay loam soils, much higher pesticide levels in particles of 0.25 and 0.5mm than thatin particle of 2. 0mm were detected, the levels in particles of 0. 1 and 1.0mm were approximatelyequal to the level in mixed soil samples, but in sandy loam, the pesticide levels increased with soilparticle sizes. Based on the photolytic rates of cypermethrin, deltamethrim, and fenvalerate in dif-ferent soil particles, the fastest photodegradation was observed in the particle size of 1.0mm andthe slowest photodegradation in the particle size of 0. 25mm, with the difference ratio of 1.64-1. 82 fold in sandy loam, and 1. 45-1.60 fold in clay loam.