Abstract: Eight new-generation BeiDou global satellites (BDS-3) had been launched into medium Earth orbit (MEO) successfully until May 2018. They constitute the BDS-3 simplest system, and transmit several new navigation signals, namely B1C, B2a, and B2b, and only 17 iGMAS tracking stations can track BDS-3 satellite signals. The 10 days real Multi-GNSS data of 17 iGMAS(international global navigation satellite system monitoring and assessment system) tracking stations are selected for quality analysis in terms of data integrity, signal to noise ratio(SNR), multipath effect, ionospheric delay and cycle slip. By comparing with the GPS L1/L5 signals and Galileo E1/E5a signals, the performance of the current BDS-3 satellites signals and the receiving capability of the iGMAS tracking stations are obtained. The results show that, there are large gross errors in pseudorange observations of iGMAS tracking stations which are equipped with GNSS_GGR receivers, and the cycle slips of several tracking stations equipped with CETC-54-GMR-4011 receivers are serious. The analysis of code multipath shows that the elevation-dependent system biases seem to be not exist for all the available signals of BDS-3 satellites. The observations quality of the BDS-3 simplest system satellites' is comparable to that of GPS L1/L5 and Galileo E1/E5a signals, which can meet the normal working requirements of BeiDou satellite navigation system.