Abstract: We first introduce GNSS precise point positioning(PPP)based on un-differentialuncombined raw pseudo-ranges and carrier phase observations(RAW-OBS-PPP).Then thedifference between the traditional PPP based on ionosphere-free dual-frequency combination(LC-PPP)and RAW-OBS-PPP is discussed and evaluated by analyzing mass data of 300IGSGPS sites during day of year 034～０４０,2012.The effects of receiver’s DCB and the preci-sion of priori-ionospheric delay on the convergence of RAW-OBS-PPP are focused and dis-cussed in details.For RAW-OBS-PPP,while global ionosphere mapping(GIM)provided byInternational GNSS Service(IGS)are used as priori-information for ionosphere delays,andthe receiver’s DCB is estimated,then the mean time is about 13.12min to take convergenceinto 10cm in both north and east components.If no receiver DCB estimated,it needs about18.48min.LC PPP and RAW-OBS-PPP have almost the same performance under the condi-tion that GIM is used for RAW-OBS-PPP.If ionosphere delays with higher precision areused as priori-information,RAW-OBS-PPP needs about 8.67min(mean value)in horizontalcomponents,which is much faster than traditional LC PPP.