Abstract: We carry out preliminary simulations of space-debris distributions in typical space regions for the manned space flights.The simulations are based on a prevalent model (ORDEM2000).Simulation results show that for a spacecraft at an altitude of 400 km and an orbital inclination between 40° and 50°,(1) its annual probability of collision with debris with sizes of decimeters to meters is on the order of magnitude of 10^-7,(2) the annual probability of collision with debris with sizes of centimeters is ~10^-6,(3) the annual probability of collision with debris with sizes of millimeters is about 4×10^-2,(4) the expected annual number of collisions with debris with sizes of ~0.1 mm is about two times,and (5) the expected annual number of collisions with debris of ~0.01 mm is about 550~600.The results should be valuable for relevant application sectors.