China has a huge air defense force. Like the rest of their armed forces, its a combination of (mostly) old stuff, with some new equipment. There are about 150 SAM (Surface-to-Air Missile) battalions. However, about 56 percent of these are Chinese versions (the HQ-2) of the Russian SA-2 systems from the 1950s. The Chinese have upgraded the SA-2 with modern electronics, an improved warhead, better rocket motors and more maneuverability. The inventory of missiles is believed to be about 10,000. However, many are older models, and many of these are probably of uncertain reliability. American electronic countermeasures can probably defeat all models of the HQ-2. Newer models of the HQ-2 have a range of 40 kilometers, and will hit the target 70 percent of the time (if there are no countermeasures.) The HQ-2 radars have a hard time dealing with stealthy aircraft, and the radar is needed to guide the missile to its target (via radio signals from the ground to the missile).
Another 12 percent of Chinese SAMs are based on the French Crotale system. These HQ-7s are short range (up to 15 kilometers) missiles that are very effective against low flying aircraft. The rest of the SAMs are based on the Russian S-300 system (roughly equal to the U.S. Patriot.) Again, there are several versions of these, from early ones that barely match the first Patriot systems, to a few battalions equipped with very formidable missiles. There are also 30 battalions of anti-aircraft guns (about 50 guns each). These are mainly twin 23mm guns or 57mm guns, plus single 85mm or 100mm guns and some weapons of other calibers. All these are radar controlled. In addition, there is an anti-aircraft militia equipped with some 1,500 battalions of guns (thats over 70,000 anti-aircraft guns). The weapons are not in the best shape, and most are quite old. The crews are poorly trained reservists, and they dont get much practice with live ammunition. However, if there were a war, most of these guns would be manned, and better trained, in a few weeks. However, a lot of the ammo reserves are old, so a lot of the shells would be duds.
In addition, all army units have anti-aircraft guns assigned, as well as portable anti-aircraft missiles. Many warships also mount fairly modern anti-aircraft missiles.
The Chinese concentrate their anti-aircraft weapons around high value targets, particularly around the capital and key military bases. Attacking aircraft, coming in high enough (over 20,000 feet) to avoid most of the guns, and with good countermeasures, could use smart bombs to do a lot of damage, with minimal risk.