Abstract Soil bio-crust exists widely in semiarid and arid regions throughout the world, specially in desert area. An experiment on effects of simulated falling dust, litter and bio-inoculation on formation of soil crust in desert was carried out in 2006 in Horqin Sand Land to understand mechanism of soil crust formation in desert. Results show that (1) the falling dust obviously promoted development of soil crust, but no linear relationship was observed between the coverage and thickness of soil crust and amount of falling dust; (2) when little (100 g m^-2) in amount, litter enhanced the effect of falling dust on development of soil crust, but reversely inhibited the effect, when it was more; (3) bio-inoculation significantly enhanced the effect, particularly the inoculation of lichen in arid environment, and of moss in relatively humid environment; (4) crust coverage was sensitive to input of extragenous substances, while crust thickness did not vary much with change in kind and amount of the input and (5) compared with illuminated and arid environment, shaded and wet environment was more conducive to development of soil crust and enhancement of the effects of inputs on crust formation.