The sequence structure of diene-styrene copolymer greatly affects the comprehensive properties of related rubber products (like styrene-butadiene rubber and similarly integrated rubber) or resin products (like styrene-butadiene resin). Living anionic polymerization has great advantages in controlling the comonomer sequence types, such as ideal block sequence, tapered block sequence, random sequence and alternating sequence. A novel conjugated diene，1,3-pentadiene (PD)，can undergo anionic copolymerization with styrenes to afford the special alternating sequence, whereas the high sequence 1,4-structure can be obtained by anionic polymerization of isoprene (IP). In this paper, the copolymerization of PD, styrene (ST) and IP was carried out in cyclohexane (containing 0.015% tetrahydrofuran) initiated by n-butyllithium (n-BuLi). The copolymerization kinetics and microstructure of the resultant copolymer were investigated in details. The results showed that (1) the homo-polymerization kinetics showed the polymerization rate was listed in this order ST>IP>>PD, and ST/IP and PD/IP binary copolymerization showed the classical "double S" curve (conversion vs time). Moreover, the ST/PD binary copolymerization rate was similar to the IP homopolymerization rate; (2) NMR and reactivity ratio data show that ST/PD binary copolymerization conforms to classical alternating copolymerization behavior. Infrared data show that the 1,4-structure content of binary copolymer is higher than 90%, and the trans-1,4-structure is higher than 85%. (3) The relationship between the conversion rate of terpolymerization and the composition of instantaneous terpolymer shows that isoprene is inserted into the ST-PD sequence with a high cis-1,4-structure, and there is no obvious ST or PD microblock sequence in the terpolymer, and thus the sequence of ST/IP/PD is almost random; (4) The ternary copolymerization showed obvious living nd controllable polymerization, and the molecular weight was highly consistent with the theoretical value, and the molecular weight distribution was all less than 1.10. (5) DSC results showed that ternary sequence copolymer was an amorphous polymer with only one Tg, indicating the possible formation of random sequence distribution of comonomers. (6) Based on the special alternating copolymerization of ST/PD, the possible ternary polymerization mechanism of ST/IP/PD was speculated.