how to get interface traffic snmp information for routers ( cisco, zte, huawei ...)?

As Nick R already mentioned, you need IF-MIB... details matter though.

You can correlate all OIDs to an interface name below by snmp walking ifName: 1.3.6.1.2.1.31.1.1.1.1.

High Speed interfaces

For high-speed interfaces (100Mbps or above) you should use 64-bit counters if the device supports them:

• ifHCInOctets: 1.3.6.1.2.1.31.1.1.1.6 (64-bit Octets in counter)
• ifHCOutOctets: 1.3.6.1.2.1.31.1.1.1.10 (64-bit Octets out counter)
• ifHCInUcastPkts: 1.3.6.1.2.1.31.1.1.1.7 (64-bit Packets in counter)
• ifHCOutUcastPkts: 1.3.6.1.2.1.31.1.1.1.11 (64-bit Packets out counter)
• ifHighSpeed: 1.3.6.1.2.1.31.1.1.1.15 (An estimate of the interface's current bandwidth in units of 1Mbps)

Low Speed interfaces

Lower speed interfaces can get by with 32-bit counters. If you use 32-bit counters on high-speed interfaces, they can wrap quickly; a 10 Mbps stream of back-to-back, full-size packets causes ifInOctets to wrap in just over 57 minutes. At 100 Mbps, the minimum wrap time is 5.7 minutes, and at 1 Gbps, the minimum is 34 seconds ^{Note 1}

• ifInOctets: 1.3.6.1.2.1.2.2.1.10 (32-bit Octets in counter)
• ifOutOctets: 1.3.6.1.2.1.2.2.1.16 (32-bit Octets out counter)
• ifInUcastPkts: 1.3.6.1.2.1.2.2.1.11 (32-bit Packets in counter)
• ifOutUcastPkts: 1.3.6.1.2.1.2.2.1.17 (32-bit Packets out counter)
• ifSpeed: 1.3.6.1.2.1.2.2.1.5 (Currently negotiated speed of the interface - Max: 4.294 Gbps)

Note 1: Quoted from Cisco's SNMP FAQ

IF-MIB should be what you are looking for. The OID you want is ifInOctets and ifOutOctets.

Cacti is the most strait forward way to go.

Download an install it, it will work with a lot of routers and switches straight out of the box. Also, Observium is even easier to get going but less customisable than Cacti; although it does also work with most switches and routers strait out of the box.

Update: Forgot to say these include the MIBs!