Three QZSS satellites were launched in 2017 and QZSS will start to provide a four‐satellite regional service from November, 2018. In this paper, we investigate the current QZSS signal in space (SIS) and the differential‐inter system bias (DISB) and inter‐frequency clock bias (IFCB) of QZSS. Currently, many IGS analysis centers provide MGEX precise orbit and clock including QZSS, 20‐days data from QZSS broadcast ephemeris and precise post‐processed orbit and clock provided by TUM(Technische Universität München) are compared, which shows that the signal is space range error (SISRE) of QZSS is 0.31m, 0.43m, 0.42m for J01, J02 and J03. Analysis results also prove that a high correlation exists between QZSS orbit and clock, which is understandable for the orbit feature of IGSO. The Allan deviation shows that the QZS rubidium atomic frequency standard (RAFS) is better than 2× 10e‐13 at an integration time of 100 seconds, which is between GPS Block IIR and Block IIF satellites. Due to the limitation of satellite number, QZSS is not enough to provide PNT service alone and it is usually combined with other GNSS systems, in which case the inter‐system bias (ISB) should be taken into account. For RTK applications, the DISB and should be calibrated between different signals. We use several short baselines installed with different kinds of receivers and estimate the DISB between QZSS and GPS. Results show that code DISB is about 1 meter for C1C comparing with C1C in GPS. For C1Z, C1X and C2L signals, it could reach 2~3 meters. As for phase DISB, QZSS L1C and L1X signal has the zero mean bias with L1C in GPS, L2L, L2X and L2S signal usually has 1/4 cycle phase bias with L2W in GPS, but the phase DISB in L1Z is not stable, which proves that the characteristic of DISB in different signal is not the same. QZSS precise or broadcast satellite clock is based on L1/L2 ionosphere combination. As QZSS provides multi‐signals of L1/L2/L5/L6, it is important to calibrate the IFCB in QZSS. We improve the traditional algorithm of IFCB estimation and estimate the IFCB between L1L2 and L1L5 in QZSS using 12 MGEX stations in two weeks. Results show that the IFCB exhibits periodic signal with a notable period of 24 hour and the amplitude is within 10cm, which is smaller than GPS. The RMS of IFCB for J01~J03 is 4.0cm, 2.8cm, 2.3cm, respectively. When apply PPP in other frequencies, this IFCB should be taken into account.