Yttria-stabilized zirconia (YSZ) coatings were deposited by low pressure plasma spray (LPPS) in 1.0 ×104 Pa,1.5 × 104 Pa,and 2.5 × 104 Pa.Both in-flight particle diagnostic detected by DPV2000 system and ANSYS-FLUENT software were used to study the connection between the parameters of flying particles and the coating formation,which might help to recognize the relationship between the operation parameters and the coatings quality.The results of simulation showed that particles in a lower spray pressure could achieve a higher velocity.The particle velocity was around 380 m/s at a distance of 35 cm from the nozzle at 1.0 × 104 Pa while only 300m/s at 2.5 × 104 Pa in actual measurement.The results showed that the velocity of particles increased with decreasing the spray pressure,which might enhance the flattening rate of coatings and thereby decreased the porosity.The deposited YSZ coating with the lowest porosity can be gained under 1.0× 104 Pa condition.